There are many participants who have contributed to the work reported in this paper, including all the members of our project team, as well as some people from the Astronauts research and training center (ACC) and Neusoft.
This work is funded by the Strategic Priority Research Program on Space Science, Chinese Academy of Sciences: SJ-10 Recoverable Scientific Experiment Satellite (Grant No. XDA04020405 and XDA04020202-05), and by the joint fund of National Natural Science Foundation of China (U1738116).

1. Design and preparation of the experimental system
<ol>
	<li>Construct the annular liquid pool.
	<ol>
		<li>Build a copper annular liquid pool measuring Ri = 4 mm in inner diameter and Ro = 20 mm in outer diameter and d = 12 mm in height.</li>
		<li>Use a polysulfone plate measuring RP = 20 mm in diameter as the bottom of the liquid pool (see Table of Materials).</li>
		<li>Drill a small hole measuring &#981; = 2 mm in diameter close to the inner wall (6 mm away from the center of the circle) as the liquid injection hole.</li>
	</ol>
	</li>
	<li>Maintain the interface.
	<ol>
		<li>Add sharp corners (45&#176; angles) on the inner and outer side walls (Figure 2).</li>
		<li>Apply anti-creeping liquid21 (see Table of Materials) to the inner and outer walls to a height greater than 12 mm.</li>
	</ol>
	</li>
	<li>Prepare the storage system of working liquid.
	<ol>
		<li>Choose 2cSt silicone oil as the working liquid (see Table of Materials).</li>
		<li>Use a hydraulic cylinder as the container for storing the silicone oil (see Table of Materials).</li>
		<li>Inject the working fluid to the hydraulic cylinder using the bubble-free technique before launch. 
		NOTE: Bubbles suspended in the working fluid will result in the failure of the experiment.
		<ol>
			<li>Discharge the gas in the silicone oil by heating the liquid to 60 &#176;C and applying pressure &#60;150 Pa for about 6 h.</li>
			<li>Vacuum the liquid storage system until its pressure is &#60;200 Pa.</li>
			<li>Relieve the valve to allow the silicone oil to fill in the vacuumed cylinder without gas (Figure 3).</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Set up the injection system for the working liquid.
	<ol>
		<li>Select a step motor to drive the injection or suction of liquid (see Table of Materials).</li>
		<li>Apply a solenoid valve to control the on-off switch of the injection system (see Table of Materials).</li>
		<li>Connect the step motor to the liquid cylinder using a universal joint (Figure 4).</li>
		<li>Connect the liquid cylinder, solenoid valve, and injection hole successively with a pipe measuring 4 mm in outer diameter.</li>
	</ol>
	</li>
</ol>
2. Establishment of the temperature control system
<ol>
	<li>Embed the inner cylinder with a heating film (resistance Rt = 14.4 &#177; 0.5 &#937;) and measure the temperature Ti with a K-type thermocouple (see Table of Materials).</li>
	<li>Symmetrically attach six refrigeration chips (every two chips are connected in parallel as a group, and three groups are connected in a series) to the outer wall and obtain the outer wall temperature To using an additional K-type thermocouple. 
	NOTE: The temperature difference is &#916;T = Ti - To.</li>
</ol>
3. Establishment of the measurement system
NOTE: All devices can be controlled by software.
<ol>
	<li>Place six thermocouples (T1 - T6) inside the liquid pool to measure temperatures at different points. The detailed layout is shown in Figure 5.</li>
	<li>Place the infrared camera directly above the liquid surface, and rotate the lens to adjust the focus and collect the temperature field information on the liquid-free surface (see Table of Materials).</li>
	<li>Adjust the displacement sensor to measure the displacement of a certain point (r = 12 mm) on the liquid surface (see Table of Materials). 
	NOTE: The laser displacement sensor is used for this payload in order to realize a 100 &#181;s high-speed sampling, which is an ultra-high precision measurement method with a resolution of 1 &#181;m, and a linearity of &#177; 0.1% F.S.</li>
	<li>Use the CCD camerato focus on the liquid surface and record the change of the free surface (see Table of Materials, Figure 6). 
	NOTE: The number of effective pixels is 752 x 582, and the minimum illumination is 1.6 Lux/F2.0.</li>
</ol>
4. Experimental process
<ol>
	<li>Start the experiment control software and turn on the power button.</li>
	<li>Perform the liquid injection.
	<ol>
		<li>Apply 12 V on the solenoid valve to open it.</li>
		<li>Turn on the motor button to push the motorat a step of 2.059 mm and inject 10,305 mL of silicone oil into the liquid pool.</li>
		<li>Turn off the solenoid valve power to close the solenoid valve.</li>
	</ol>
	</li>
	<li>Perform linear heating.
	<ol>
		<li>Set the experimental conditions as follows: heating target temperature Ti = 50 &#176;C; cooling target temperature To = 15 &#176;C; and heating rate = 0.5 &#176;C/min.</li>
	</ol>
	</li>
	<li>Collect data.
	<ol>
		<li>Set the corresponding sampling frequencies of the infrared imager, thermocouples, displacement sensor, and CCD to 7.5 Hz, 20 Hz, 20 Hz, and 25 Hz respectively.</li>
		<li>Click the button for the data collecting system and monitor the temperature, displacement, and other information using the computer software (Figure 7).</li>
	</ol>
	</li>
	<li>Turn off the power button. 
	NOTE: Wait 1 h so that the temperatures of the hot and cold ends are equal to the ambient temperature for the following experiment.</li>
</ol>

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	<li>Scriven, L. E., Sternling, C. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Marangoni+effect.">The Marangoni effect.</a> Nature. 187, 186-188 (1960).</li><li>Effects of heating mode on steady antisymmetric thermocapillary flows in microgravity. Heat Transfer in Microgravity Systems, Trans. American Society of Mechanical Engineers Available from: <a target="_blank" href="https://heattransfer.asmedigitalcollection.asme.org/">https://heattransfer.asmedigitalcollection.asme.org/</a> (1994)</li><li>Benz, S., Schwabe, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+three-dimensional+stationary+instability+in+dynamic+thermocapillary+shallow+cavities.">The three-dimensional stationary instability in dynamic thermocapillary shallow cavities.</a> Experiments in Fluids. 31, 409-416 (2001).</li><li>Schwabe, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Buoyant-thermocapillary+and+pure+thermocapillary+convective+instabilities+in+Czochralski+systems.">Buoyant-thermocapillary and pure thermocapillary convective instabilities in Czochralski systems.</a> Journal of Crystal Growth. 237-239, 1849-1853 (2002).</li><li>Kamotani, Y., Ostrach, S., Pline, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+velocity+data+taken+in+surface+tension+drivenconvection+experiment+in+microgravity.">Analysis of velocity data taken in surface tension drivenconvection experiment in microgravity.</a> Physics of Fluids. 6, 3601-3609 (1994).</li><li>Kamotani, Y., Ostrach, S., Pline, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+thermocapillary+convection+experiment+in+microgravity.">A thermocapillary convection experiment in microgravity.</a> Journal of Heat Transfer. 117, 611-618 (1995).</li><li>Kamotani, Y., Ostrach, S., Pline, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Some+temperature+field+results+from+the+thermocapillary+flow+experiment+aboard+USML-2+spacelab.">Some temperature field results from the thermocapillary flow experiment aboard USML-2 spacelab.</a> Advances in Space Research. 22, 1189-1195 (1998).</li><li>Kamotani, Y., Ostrach, S., Masud, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microgravity+experiments+and+analysis+of+oscillatory+thermocapillary+flows+in+cylindrical+containers.">Microgravity experiments and analysis of oscillatory thermocapillary flows in cylindrical containers.</a> Journal of Fluid Mechanics. 410, 211-233 (2000).</li><li>Schwabe, D., Benz, S., Cramer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experiment+on+the+Multi-roll-structure+of+thermocapillary+flow+in+side-heated+thin+liquid+layers.">Experiment on the Multi-roll-structure of thermocapillary flow in side-heated thin liquid layers.</a> Advances in Space Research. 24 (10), 1367-1373 (1999).</li><li>Schwabe, D., Benz, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermocapillary+flow+instabilities+in+an+annulus+under+microgravity+results+of+the+experiment+MAGIA.">Thermocapillary flow instabilities in an annulus under microgravity results of the experiment MAGIA.</a> Advances in Space Research. 29, 629-638 (2002).</li><li>Kawamura, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Report+on+Microgravity+Experiments+of+Marangoni+Convection+Aboard+International+Space+Station.">Report on Microgravity Experiments of Marangoni Convection Aboard International Space Station.</a> Journal of Heat Transfer. 134 (3), 031005 (2012).</li><li>Sato, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrothermal+Wave+Instability+in+a+High-Aspect-Ratio+Liquid+Bridge+of+Pr+&gt;+200.">Hydrothermal Wave Instability in a High-Aspect-Ratio Liquid Bridge of Pr &gt; 200.</a> Microgravity Science and Technology. 25 (1), 43-58 (2013).</li><li>Yano, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Instability+and+associated+roll+structure+of+Marangoni+convection+in+high+Prandtl+number+liquid+bridge+with+large+aspect+ratio.">Instability and associated roll structure of Marangoni convection in high Prandtl number liquid bridge with large aspect ratio.</a> Physics of Fluids. 27 (2), 024108 (2015).</li><li>Yao, Y. L., Liu, Q. S., Zhang, P., Hu, L., Liu, F., Hu, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Space+Experiments+on+Thermocapillary+Convection+and+Marangoni+Convection+in+Two+Immiscible+Liquid+Layers.">Space Experiments on Thermocapillary Convection and Marangoni Convection in Two Immiscible Liquid Layers.</a> Journal of the Japan Society of Microgravity Application. 15, 394-398 (1998).</li><li>Zhang, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Space+experimental+device+on+Marangoni+drop+migrations+of+large+Reynolds+numbers.">Space experimental device on Marangoni drop migrations of large Reynolds numbers.</a> Science in China. 44 (6), 605-614 (2001).</li><li>Xie, J. C., Lin, H., Zhang, P., Liu, F., Hu, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+investigation+on+thermocapillary+drop+migration+at+large+Marangoni+number+in+reduced+gravity.">Experimental investigation on thermocapillary drop migration at large Marangoni number in reduced gravity.</a> Journal of Colloid and Interface Science. 285, 737-743 (2005).</li><li>Kang, Q., Cui, H. L., Hu, L., Duan, L., Hu, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+Investigation+on+bubble+coalescence+under+non-uniform+temperature+distribution+in+reduced+gravity.">Experimental Investigation on bubble coalescence under non-uniform temperature distribution in reduced gravity.</a> Journal of Colloid and Interface Science. 310, 546-549 (2007).</li><li>Duan, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+real-time+March-Zehnder+interferometer+used+in+space+experiment.">The real-time March-Zehnder interferometer used in space experiment.</a> Microgravity Science and Technology. 20, 91-98 (2008).</li><li>Zhu, P., Zhou, B., Duan, L., Kang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+of+surface+oscillation+in+thermocapillary+convection.">Characteristics of surface oscillation in thermocapillary convection.</a> Experimental Thermal and Fluid Science. 35, 1444-1450 (2011).</li><li>Zhu, P., Duan, L., Kang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transition+to+chaos+in+thermocapillary+convection.">Transition to chaos in thermocapillary convection.</a> International Journal of Heat and Mass Transfer. 57, 457-464 (2013).</li><li>Kang, Q., Duan, L., Zhang, L., Yin, Y. 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We have nothing to disclose.

Due to the limitation of space resources, the volume of the equipment as a whole is only 400 mm &#215; 352 mm &#215; 322 mm, with a weight of only 22.9 &#177; 0.2 kg. This is very inconvenient when selecting and laying out experimental devices, and the establishment of the flow system becomes the critical step. Therefore, the increasing temperature difference is set at two ends of the liquid pool so that the fluid can generate a series of flow phenomena. In order to observe the entire process of the convection from stead...

Under microgravity conditions in space, many interesting physical phenomena are presented due to the absence of gravity. In a liquid with a free surface, there exists a new flow system (i.e. thermocapillary flow) that is caused by the temperature gradient or concentration gradient. Different from traditional convection on the ground, thermocapillary convection is a ubiquitous phenomenon in space environments. As it is a very important research subject in microgravity fluid physics, a number of experiments have been carried out in space as well as on the ground. Recently, space experimental studies were performed on thermocapillary convection on the SJ-10 recoverable scientific experiment satellite. The space experiment payload consisted of eight systems, namely a fluid experiment system, liquid storage and injection system, temperature control system, thermocouple measurement system, infrared thermal camera, displacement sensors, CCD image acquisition system, and electrical control system, as shown in Figure 1 (left). The space experiment payload for research on surface waves of thermocapillary convection is shown in Figure 1 (right). This study focused on the instability of flow, oscillation phenomena, and transitions, which are important characteristics in the transition process from laminar flow to chaos. Studies on these fundamental subjects have great significance for research regarding strong nonlinear flow.
Unlike buoyancy convection driven by volume force, thermocapillary convection is a phenomenon caused by surface tension within the interface between two immiscible fluids. The magnitude of surface tension changes with some scalar parameters, including temperature, solute concentration, and electric field strength. When these scalar fields distribute unevenly in the interface, there will be a surface tension gradient present on the free surface. The fluid on the free surface is driven by the surface tension gradient to move from the location with lesser surface tension to that with greater surface tension. This flow was first interpreted by an Italian physicist, Carlo Marangoni. Hence, it was named the &#34;Marangoni effect&#34;1. Marangoni flow on the free surface extends to the inner liquid by viscosity and as a result generates what is known as Marangoni convection.
Strictly speaking, for the fluid system with a free surface, thermocapillary convection and buoyancy convection always appear simultaneously under normal gravity. In general, for a macroscopic convective system, thermocapillary convection is a minor effect and is usually ignored in comparison with buoyancy convection. However, under the condition of a small-scale convective system or in the microgravity environment, buoyancy convection will be greatly weakened, or even disappear, and thermocapillary convection will become dominant in the flow system. For a long period of time, research has been focused on macro-scale buoyancy convection due to the limitations in human activities and research methods2,3,4. However, in recent decades, with the rapid development of modern science and technology such as aerospace, film, MEMS, and nonlinear science, the need for further research on thermocapillary convection has become increasingly urgent.
Studies regarding microgravity hydrodynamics have important academic significance and application prospects. Many dynamicists, physical chemists, biologists, and materials scientists have gathered to work in this field. Kamotani and Ostrach completed experiments on thermocapillary convection in an annular liquid pool under microgravity conditions2,5,6,7,8 and observed steady flow, oscillatory flow, and critical conditions. Schwabe et al. studied buoyant-thermocapillary convection in a similar annular liquid pool3,9 and found that the oscillatory flow first appeared as thermocapillary waves, and then turned to a more complex flow with the increase in temperature difference. In 2002, Schwabe and Benz et al. reported a group of experiments on thermocapillary convection in an annular liquid pool carried out on the Russian FOTON-12 satellite4,10. Their space experimental results were consistent with ground experimental results. Some Japanese scientists carried out three series of experiments on liquid bridge thermocapillary convection, named the Marangoni Experiment in Space (MEIS), on the International Space Station11,12,13. Some experimental equipment, including the camera, thermal imager, thermocouple sensors, and 3D-PTV and photochromic technology, were applied in these three tasks. The critical conditions of thermocapillary convection at different aspect ratios were determined, and three-dimensional (3D) flow structures were observed.
Over the past 30 years, microgravity science has undergone prolific development in China14,15,16, and a number of microgravity experiments have been conducted in space17,18. In the field of fluid physics, the first microgravity experiment was the study of two-layer fluid on the SJ-5 recoverable satellite in 1999, and the flow structure was obtained by the particle tracing method14. In 2004, the study on thermocapillary migration of a droplet was carried out on the SZ-4, and the relationship between migration velocity and critical Mach (Ma) number was obtained15,16. In 2005, the experimental study on multi-bubble thermocapillary migration was carried out on the JB-417, and the migration rules were obtained as the Ma number was increased to 8,000. Meanwhile, problems such as bubble merging were also studied. In 2006, the study on diffusion mass transfer was carried out on the SJ-8 recoverable satellite, the Mach-Zehnder interferometer was first applied in the space experiment, the process of diffusion mass transfer was observed, and the diffusion coefficient was evaluated18.
In recent years, a series of ground experimental studies focused on oscillation and bifurcation processes in thermocapillary convection have been carried out, and the coupled effect of buoyancy and thermocapillary force has been analyzed. Experimental results show that the buoyancy effect cannot be ignored in ground experiments, as it plays a dominant role in many cases19,20,21,22. In 2016, two microgravity experiments were carried out to research thermocapillary convection in the liquid bridge on the TG-2, and thermocapillary convection in the annular liquid pool on the SJ-10 recoverable satellite23,24. The present paper introduces the experimental payload of thermocapillary convection on the SJ10, and the space experiment results. These methods will be helpful in exploring the mechanism of thermocapillary oscillation.
In order to observe the convective pattern transition, temperature oscillation, and liquid-free surface deformation, six thermocouples, an infrared thermal camera, and a displacement sensor to quantify the frequency, amplitude, and other physical quantities of the oscillation were used. Through investigations on oscillation and transition in thermocapillary convection in space, the mechanism of thermocapillary convection in the microgravity environment, which provides scientific guidance for the growth of materials in space, can be discovered and understood. Furthermore, technological breakthroughs in such space experiments, such as the techniques of liquid surface maintenance and liquid injection without bubbles, will further enhance the simplicity and technical level of microgravity experiments in fluid physics.
This paper introduces the payload development and space experiment of the thermocapillary surface wave project carried out on the SJ-10 scientific experimental satellite. As a space experiment payload, this thermocapillary convection system has a strong anti-vibration ability to prevent violent shock, especially during the satellite launching process. In order to meet the requirements of remote operation, the space experiment process is controlled automatically, and the space experimental data can be transmitted to the Ground Signal Receiving Station of the Spacecraft and then to the scientists&#39; experimental platform.

<table><tbody><tr><td>anti-creeping liquid</td><td>3M</td><td>EGC-1700</td><td></td></tr><tr><td>CCD</td><td>WATTEC</td><td>WAT-230VIVID</td><td></td></tr><tr><td>Displacement sensor</td><td>Panasonic</td><td>HL-C1</td><td></td></tr><tr><td>Heating film</td><td>HongYu</td><td>125 Q/W335.1A</td><td></td></tr><tr><td>Hydraulic cylinder</td><td>FESTO</td><td>ADVU-40-25-P-A</td><td></td></tr><tr><td>Infrared camera</td><td>FLIR</td><td>Tau2</td><td></td></tr><tr><td>LED</td><td>693 Institute</td><td>10257MW7C</td><td></td></tr><tr><td>Montor</td><td>PI</td><td>M-227</td><td></td></tr><tr><td>Montor controller</td><td>PI</td><td>C-863</td><td></td></tr><tr><td>Pipe, 4mm</td><td>FESTO</td><td>PUN-4X0,75-GE</td><td></td></tr><tr><td>polysulfone plate</td><td>507 Institute</td><td></td><td></td></tr><tr><td>Refrigeration chip</td><td>Zhongke</td><td>9502/065/021M</td><td></td></tr><tr><td>Silicon oil, 2cSt</td><td>Shin-Etsu</td><td>KF-96</td><td></td></tr><tr><td>Solenoid</td><td>FESTO</td><td>MFH-2-M5</td><td></td></tr><tr><td>Temperature controller</td><td>Eurotherm</td><td>3304</td><td></td></tr><tr><td>Thermocouple, K-type</td><td>North University of China</td><td>ZBDX-HTTK</td><td></td></tr></tbody></table>

thermocapillary convection space experiment on the sj-10 recoverable satellite

Thermocapillary convection is an important research subject in microgravity fluid physics. The experimental study on surface waves of thermocapillary convection in an annular liquid pool is one of the 19 scientific experimental projects on the SJ-10 recoverable satellite. Presented is a design for a payload for space experimental study on thermocapillary convection that includes the experimental model, measurement system, and control system. The specifics for the construction of an experimental model of an annular liquid pool with variable volume ratios is provided. The fluid temperatures are recorded by six thermocouples with a high sensitivity of 0.05 &#176;C at different points. The temperature distributions on the liquid free surface are captured by means of an infrared thermal camera. The free surface deformation is detected by a displacement sensor with a high accuracy of 1 &#181;m. The experimental process is fully automated. The research is focused on thermocapillary oscillation phenomena on the liquid-free surface and convective pattern transitions through analyses of experimental data and images. This research will be helpful to understand the mechanism of thermocapillary convection and will offer further insights into the nonlinear characteristics, flow instability, and bifurcation transitions of thermocapillary convection.

The accurate volume ratio was defined, and the liquid surface topography was reconstructed based on the images captured by the CCD. The critical instability condition was determined, and the oscillation characteristics were studied through analyses on single point temperature signals and displacement oscillating signals. The structure of the flow field was obtained, and the transition of the flow pattern was determined through the change of the infrared image with time. The flow character...

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Thermocapillary Convection Space Experiment on the SJ-10 Recoverable Satellite

A protocol for the space payload design, the space experiment on thermocapillary convection, and analyses of experimental data and images are presented in this paper.

Thermocapillary convection is an important research subject in microgravity fluid physics. The experimental study on surface waves of thermocapillary ...

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6.5K Views.  Chinese Academy of Sciences. A protocol for the space payload design, the space experiment on thermocapillary convection, and analyses of experimental data and images are presented in this paper.

Video: Thermocapillary Convection Space Experiment on the SJ-10 Recoverable Satellite

Exploring the Effects of Atmospheric Forcings on Evaporation: Experimental Integration of the Atmospheric Boundary Layer and Shallow Subsurface

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study evaporation under various surface boundary conditions to improve our current understanding and characterization of this multiphase phenomenon as well as to validate numerical heat and mass transfer theories that couple Navier-Stokes flow in the atmosphere and Darcian flow in the porous media. Experimental data were collected using a unique soil tank apparatus interfaced with a small climate controlled wind tunnel. The experimental apparatus was instrumented with a suite of state of the art sensor technologies for the continuous and autonomous collection of soil moisture, soil thermal properties, soil and air temperature, relative humidity, and wind speed. This experimental apparatus can be used to generate data under well controlled boundary conditions, allowing for better control and gathering of accurate data at scales of interest not feasible in the field. Induced airflow at several distinct wind speeds over the soil surface resulted in unique behavior of heat and mass transfer during the different evaporative stages.

A protocol for the design and construction of a soil tank interfaced to a small climate controlled wind tunnel to study the effects of atmospheric forcings on evaporation is presented. Both the soil tank and wind tunnel are instrumented with sensor technologies for the continuous in situ measurement of environmental conditions.

Evaporation is directly influenced by the interactions between the atmosphere, land surface and soil subsurface. This work aims to experimentally study ...

Environment

Experimental System of Solar Adsorption Refrigeration with Concentrated Collector

To improve the performance of solar adsorption refrigeration, an experimental system with a solar concentration collector was set up and investigated. The main components of the system were the adsorbent bed, the condenser, the evaporator, the cooling sub-system, and the solar collector. In the first step of the experiment, the vapor-saturated bed was heated by the solar radiation under closed conditions, which caused the bed temperature and pressure to increase. When the bed pressure became high enough, the bed was switched to connect to the condenser, thus water vapor flowed continually from the bed to the condenser to be liquefied. Next, the bed needed to cool down after the desorption. In the solar-shielded condition, achieved by aluminum foil, the circulating water loop was opened to the bed. With the water continually circulating in the bed, the stored heat in the bed was took out and the bed pressure decreased accordingly. When the bed pressure dropped below the saturation pressure at the evaporation temperature, the valve to the evaporator was opened. A mass of water vapor rushed into the bed and was adsorbed by the zeolite material. With the massive vaporization of the water in the evaporator, the refrigeration effect was generated finally. The experimental result has revealed that both the COP (coefficient of the performance of the system) and the SCP (specific cooling power of the system) of the SAPO-34 zeolite was greater than that of the ZSM-5 zeolite, no matter whether the adsorption time was longer or shorter. The system of the SAPO-34 zeolite generated a maximum COP of 0.169.

With solar energy as the driving force, a novel adsorption refrigeration system has been developed and experimentally investigated. Water vapor and zeolite formed the working pair of the adsorption system. This manuscript describes the setup of the experimental rig, the operation procedure, and the important results.

To improve the performance of solar adsorption refrigeration, an experimental system with a solar concentration collector was set up and investigated. The ...

Thermal Scanning Conductometry (TSC) as a General Method for Studying and Controlling the Phase Behavior of Conductive Physical Gels

The thermal scanning conductometry protocol is a new approach in studying ionic gels based on low molecular weight gelators. The method is designed to follow the dynamically changing state of the ionogels, and to deliver more information and details about the subtle change of conductive properties with an increase or decrease in the temperature. Moreover, the method allows the performance of long term (i.e. days, weeks) measurements at a constant temperature to investigate the stability and durability of the system and the aging effects. The main advantage of the TSC method over classical conductometry is the ability to perform measurements during the gelation process, which was impossible with the classical method due to temperature stabilization, which usually takes a long time before the individual measurement. It is a well-known fact that to obtain the physical gel phase, the cooling stage must be fast; moreover, depending on the cooling rate, different microstructures can be achieved. The TSC method can be performed with any cooling/heating rate that can be assured by the external temperature system. In our case, we can achieve linear temperature change rates between 0.1 and approximately 10 &#176;C/min. The thermal scanning conductometry is designed to work in cycles, continuously changing between heating and cooling stages. Such an approach allows study of the reproducibility of the thermally reversible gel-sol phase transition. Moreover, it allows the performance of different experimental protocols on the same sample, which can be refreshed to initial state (if necessary) without removal from the measuring cell. Therefore, the measurements can be performed faster, in a more efficient way, and with much higher reproducibility and accuracy. Additionally, the TSC method can be also used as a tool to manufacture the ionogels with targeted properties, like microstructure, with an instant characterization of conductive properties.

Thermal Scanning Conductometry TSC as a General Method for Studying and Controlling the Phase Behavior of Conductive Physical Gels

The kinetics of the cooling process defines the properties of ionic gels based on low molecular weight gelators. This manuscript describes the usage of thermal scanning conductometry (TSC), which obtains full control over the gelation process, along with in situ measurements of the samples' temperature and conductivity.

The thermal scanning conductometry protocol is a new approach in studying ionic gels based on low molecular weight gelators. The method is designed to ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Simulation of Early Earth Hydrothermal Chimneys in a Thermal Gradient Environment

Deep sea hydrothermal vents are self-organizing precipitates generated from geochemical disequilibria and have been proposed as a possible setting for the emergence of life. The growth of hydrothermal chimneys in a thermal gradient environment within an early Earth vent system was successfully simulated by using different hydrothermal simulants, such as sodium sulfide, which were injected into an early Earth ocean simulant containing dissolved ferrous iron. Moreover, an apparatus was developed to sufficiently cool the ocean simulant to near 0 &#176;C in a condenser vessel immersed in a cold water bath while injecting a sulfide solution at hot to room temperatures, effectively creating an artificial chimney structure in a temperature gradient environment over a period of a few hours. Such experiments with different chemistries and variable temperature&#160;gradients resulted in a variety of morphologies in the chimney structure. The use of ocean and hydrothermal fluid simulants at room temperature resulted in vertical chimneys, whereas the combination of a hot hydrothermal fluid and cold ocean simulant inhibited the formation of robust chimney structures. The customizable 3D printed condenser created for this study acts as a jacketed reaction vessel that can be easily modified and used by different researchers. It will allow the careful control of injection rate and chemical composition of vent and ocean simulants, which should help accurately simulate prebiotic reactions in chimney systems with thermal gradients similar to those of natural systems.

The goal of this protocol is to form simulated hydrothermal chimneys via chemical garden injection experiments and introduce a thermal gradient across the inorganic precipitate membrane, using a 3D printable condenser that can be reproduced for educational purposes.

Deep sea hydrothermal vents are self-organizing precipitates generated from geochemical disequilibria and have been proposed as a possible setting for the ...

Experimental Methods for Efficient Solar Hydrogen Production in Microgravity Environment

Long-term space flights and cis-lunar research platforms require a sustainable and light life-support hardware which can be reliably employed outside the Earth's atmosphere. So-called 'solar fuel' devices, currently developed for terrestrial applications in the quest for realizing a sustainable energy economy on Earth, provide promising alternative systems to existing air-revitalization units employed on the International Space Station (ISS) through photoelectrochemical water-splitting and hydrogen production. One obstacle for water (photo-) electrolysis in reduced gravity environments is the absence of buoyancy and the consequential, hindered gas bubble release from the electrode surface. This causes the formation of gas bubble froth layers in proximity to the electrode surface, leading to an increase in ohmic resistance and cell-efficiency loss due to reduced mass transfer of substrates and products to and from the electrode. Recently, we have demonstrated efficient solar hydrogen production in microgravity environment, using an integrated semiconductor-electrocatalyst system with p-type indium phosphide as the light-absorber and a rhodium electrocatalyst. By nanostructuring the electrocatalyst using shadow nanosphere lithography and thereby creating catalytic 'hot spots' on the photoelectrode surface, we could overcome gas bubble coalescence and mass transfer limitations and demonstrated efficient hydrogen production at high current densities in reduced gravitation. Here, the experimental details are described for the preparations of these nanostructured devices and further on, the procedure for their testing in microgravity environment, realized at the Bremen Drop Tower during 9.3 s of free fall.

Efficient solar-hydrogen production has recently been realized on functionalized semiconductor-electrocatalyst systems in a photoelectrochemical half-cell in microgravity environment at the Bremen Drop Tower. Here, we report the experimental procedures for manufacturing the semiconductor-electrocatalyst device, details of the experimental set-up in the drop capsule and the experimental sequence during free fall.

Long-term space flights and cis-lunar research platforms require a sustainable and light life-support hardware which can be reliably employed outside the ...

Chemistry

Couette Flow

Couette flow represents the flow of fluid between two parallel plates, with one plate fixed and the other moving with a constant velocity. This configuration allows for a simplified analysis using the Navier-Stokes equations, which govern fluid motion under conditions of viscosity and incompressibility. For Couette flow, the assumptions include a steady, laminar, incompressible flow with a zero-pressure gradient in the flow direction. This flow type is beneficial for understanding shear-driven flows and is relevant to applications in lubrication and civil engineering scenarios such as sediment transport and erosion.
In a Couette flow setup, let the x-axis align with the moving direction of the upper plate while the y-axis is perpendicular to both plates. The flow is steady, laminar, and fully developed, with no variation in the
For Couette flow, the velocity distribution equation is given by:
<img alt="Equation 1" src="/files/ftp_upload/18064/18064_Equation_1.svg" style="text-align: center; height: 30px;" />
Where:
<ol style="list-style-type: circle;">
	<li>U is the constant velocity of the upper plate,</li>
	<li>b is the distance between the plates,</li>
	<li>&#956; is the dynamic viscosity of the fluid.</li>
</ol>
In dimensionless form, dividing both sides by U, we get:
<img alt="Equation 2" src="/files/ftp_upload/18064/18064_Equation_2.svg" style="text-align: center; height: 30px;" />
Where u/U represents the dimensionless velocity, and y/b represents the normalized distance from the stationary plate. To analyze specific conditions, we define the dimensionless parameter P as:
<img alt="Equation 3" src="/files/ftp_upload/18064/18064_Equation_3.svg" style="text-align: center; height: 30px;" />
Under these conditions, P becomes zero when there is no pressure gradient (&#8706;p/&#8706;x=0) in the x-direction, reducing the velocity equation to:
<img alt="Equation 4" src="/files/ftp_upload/18064/18064_Equation_4.svg" style="text-align: center; height: 26px;" />
This linear profile indicates that the fluid velocity increases linearly from zero at the stationary plate to U at the moving plate, resulting in a uniform shear rate across the fluid layer.

Couette flow describes fluid motion between two parallel plates where one is stationary, and the other moves with constant speed, creating a steady, ...

Civil Engineering

Differential Analysis of Fluid Flow

KEY TERMS AND CONCEPTS

Constant Pressure Calorimetry

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a substance. The heat is exchanged with a calibrated and insulated device called the calorimeter. Calorimetry experiments are based on the assumption that there is no heat exchange between the insulated calorimeter and the external environment. The well-insulated calorimeters prevent the transfer of heat between the calorimeter and its external environment, which effectively limits the &ldquo;surroundings&rdquo; to the nonsystem components within the calorimeter (and the calorimeter itself). This enables the accurate determination of the heat involved in chemical processes, such as the energy content of foods.&nbsp;
The temperature change measured by the calorimeter is used to derive the amount of heat transferred by the process under study. In a calorimeter, a system is defined as the substance or substances undergoing the chemical or physical change, or in other words, the reaction, and the surroundings are all other matter, including the solution and any other components in the calorimeter that either provide heat to the system or absorb heat from the system.
Before discussing the calorimetry of chemical reactions, consider a simpler example that illustrates the core idea behind calorimetry. Suppose a hot piece of metal at a high-temperature is placed in a low-temperature substance, such as cool water. Heat will flow from the hot metal to the water. The temperature of the metal will decrease, and the temperature of the water will increase until the two substances have the same temperature&mdash;that is when they reach thermal equilibrium. If this occurs in a calorimeter, all of the heat is transferred between the two substances, with no heat gained or lost by its external environment. Under these ideal circumstances, the net heat change is zero:
<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/798/798_Equations-01.png" style="height: 40px;" />
This relationship can be rearranged to show that the heat gained by the metal is equal to the heat lost by substance the water:
<img alt="Eq2" src="https://www.jove.com/files/core/CDNSource/lessons/798/798_Equations-02.png" style="height: 40px;" />
The magnitude of the heat (change) is, therefore, the same for both substances. The negative sign merely shows that qmetal and qwater are opposite in direction of&nbsp;heat flow (gain or loss), but it does not indicate the arithmetic sign of either q value (that is determined by whether the matter in question gains or loses heat, per definition). In the specific situation described, qmetal is a negative value and qwater is a positive value since heat is transferred from the metal to the water.
When using calorimetry to determine the heat involved in a chemical reaction, the same principles apply. The amount of heat absorbed by the calorimeter is often small enough that it can most often be neglected, and the calorimeter minimizes energy exchange with the outside environment. When an exothermic reaction occurs in solution in a calorimeter, the heat produced by the reaction is absorbed by the solution, which increases its temperature. When an endothermic reaction occurs, the heat required is absorbed from the thermal energy of the solution, which decreases its temperature. The temperature change (&Delta;T), along with the specific heat (csoln) and mass of the solution (msoln), can then be used to calculate the amount of heat (qsoln) involved in either case.
<img alt="Eq3" src="https://www.jove.com/files/core/CDNSource/lessons/798/798_Equations-03.png" style="height: 40px;" />
A &nbsp;simple calorimeter &mdash; called the coffee cup calorimeter &mdash; is constructed from two nested polystyrene cups closed with a loose-fitting lid. Coffee cup calorimeters are used to measure the heat of reactions that take place in solutions (mostly aqueous solutions) and involve no or very little volume change. Because energy is neither created nor destroyed during a chemical reaction, the heat produced or consumed in the reaction (the &ldquo;system&rdquo;), qrxn, plus the heat absorbed or lost by the solution (the &ldquo;surroundings&rdquo;), qsoln, must add up to zero:
<img alt="Eq4" src="https://www.jove.com/files/core/CDNSource/lessons/798/798_Equations-04.png" style="height: 40px;" />
This means that the amount of heat produced or consumed in the reaction equals the amount of heat absorbed or lost by the solution:
<img alt="Eq5" src="https://www.jove.com/files/core/CDNSource/lessons/798/798_Equations-05.png" style="height: 40px;" />
The coffee cup calorimeter is a constant-pressure calorimeter, and the measured heat of the reaction is equivalent to the change in enthalpy.
<img alt="Eq6" src="https://www.jove.com/files/core/CDNSource/lessons/798/798_Equations-06.png" style="height: 40px;" />
This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/5-2-calorimetry">Openstax, Chemistry 2e, Section 5.2: Calorimetry</a>.

Constant Pressure Calorimeter/ Coffee Cup Calorimeter

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a ...

Thermochemistry

Constant Volume Calorimetry

Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant (atmospheric) pressure and are convenient to measure heat flow (or enthalpy change) accompanying processes that occur in solution at constant pressure. A different type of calorimeter that operates at constant volume, colloquially known as a bomb calorimeter, is used to measure the energy produced by reactions that yield large amounts of heat and gaseous products, such as combustion reactions. (The term &ldquo;bomb&rdquo; comes from the observation that these reactions can be vigorous enough to resemble explosions that would damage other calorimeters.)&nbsp;

The first law of thermodynamics suggests that the change in internal energy (&Delta;E) of a reaction is the sum of heat (q) and work (w).&nbsp;

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/797/797_Equations-01.png" style="height: 40px;" />

In gaseous reactions, the work done is pressure-volume type, thereby resulting in changes in the volume of the reaction.&nbsp;

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/797/797_Equations-02.png" style="height: 40px;" />

Bomb calorimeters are designed to operate at constant volume, such that the volume of the reaction is not allowed to change (&Delta;V = 0).&nbsp;

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/797/797_Equations-03.png" style="height: 40px;" />

Therefore, the work done is zero, and the heat (qv) measured using a bomb calorimeter is equivalent to the change in internal energy of the reaction.

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/797/797_Equations-04.png" style="height: 40px;" />

A bomb calorimeter consists of a robust steel container that contains the reactants and is itself submerged in water. The sample is placed in the bomb, which is then filled with oxygen at high pressure. A small electrical spark is used to ignite the sample. The energy produced by the reaction is absorbed by the steel bomb and the surrounding water. The temperature increase (&Delta;T) is measured and, along with the known heat capacity of the calorimeter (Ccal), is used to calculate the heat absorbed by the entire calorimeter assembly (qcal).&nbsp;

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/797/797_Equations-05.png" style="height: 40px;" />

Since the calorimeter is insulated and no heat is lost to the environment, heat gained by the calorimeter equals the heat released by the reaction.

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/797/797_Equations-06.png" style="height: 40px;" />

Due to constant volume conditions, the heat evolved in the reaction corresponds to the internal energy change.

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/797/797_Equations-07.png" style="height: 40px;" />

This is the internal energy change for the specific amount of reactant undergoing combustion. &Delta;Erxn per mole of a particular reactant is obtained by dividing the value by the number of moles that actually reacted.

Bomb calorimeters require calibration to determine the heat capacity of the calorimeter and ensure accurate results. The calibration is accomplished using a reaction with a known q, such as a measured quantity of benzoic acid ignited by a spark from a nickel fuse wire that is weighed before and after the reaction. The temperature change produced by the known reaction is used to determine the heat capacity of the calorimeter. The calibration is generally performed each time before the calorimeter is used to gather research data.

This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/5-2-calorimetry">Openstax, Chemistry 2e, Section 5.2: Calorimetry.</a>

Constant Volume Calorimeter/ Bomb Calorimeter

Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant ...

Thermosensation

Peripheral thermosensation is the perception of external temperature. A change in temperature (on the surface of the skin and other tissues) is detected by a family of temperature-sensitive ion channels called Transient Receptor Potential, or TRP, receptors. These receptors are located on free nerve endings. Those detecting cold temperatures are closer to the surface of the skin than the nerve endings detecting warmth. These thermoTRP channels, while temperature selective, have relatively non-selective cation permeability.

<h4>Cold Receptors</h4>

There are at least three types of receptors that are activated by cold, of which TRPM8 and TRPA1 are particularly sensitive. TRPM8 has a temperature sensitive range of about 10-26 oC (50-79 oF), and is largely associated with the perception of non-painful, or innocuous, cold. Menthol, a compound found in mint leaves, can also activate this receptor, which helps explain why this flavor is often perceived as cool. When temperatures are low enough to feel painful (i.e., noxious cold), TRPA1 receptors are activated. TRPA1 receptors respond to any temperature lower than 17 oC (~63 oF).

<h4>Hot Receptors</h4>

There are at least seven receptors that respond to heat. Of these, five respond to temperatures in the innocuous warmth range: TRPM2 (23-38 oC, or ~73-100oF), TRPC5 (26-38 oC, or ~79-100oF, TRPV4 (27-34 oC, or ~81-93 oF), TRPV3 (33-40 oC, or ~91-104 oF), and TRPM3 (&gt; 40 oC, or 104 oF). Painful (i.e., noxious) heat is detected by TRPV1 receptors, which respond to temperatures greater than 42 oC (~108 oF). The TRPV1 receptor was first discovered because it responds well to capsaicin, a compound found in chili peppers. Like menthol and cold, capsaicin provides the perception of heat without changing the temperature. TRPV2 receptors respond to very hot and painful temperatures (i.e., extreme noxious heat), those greater than 52 oC (~126 oF).

<h4>Transduction and Signaling Paths</h4>

Temperature information is transduced into electrical signals in the nerve endings. When nerves carry temperature information, the innocuous warm and cold information is kept separate until it reaches the brain. Cold signals are carried by dedicated myelinated A&delta; fibers that perpetuate signals quickly, as well as slower, unmyelinated C-fibers. Warmth signals are carried by their own unmyelinated C-fibers. Like touch information, temperature information from the left side of the body is processed in the right brain hemisphere. The signal decussates in the spinal cord before being relayed to the hypothalamus. There, the information is used to regulate or adjust bodily functions, like shivering or sweating. Innocuous warm and cold signals are finally relayed to several cortical areas&mdash;notably the orbitofrontal cortex.

Painful temperature information takes a separate path, using C and A&delta; fibers that are not temperature specific and can carry both hot and cold signals. Like innocuous temperature signals, they decussate in the spinal cord and are sent to the hypothalamus. From the hypothalamus, the information is sent to the anterior cingulate cortex, which generates the perception of painful cold or hot.

Studies suggest that individuals first consciously detect a feeling of coldness and warmness at about 31 oC and 34 oC, respectively. The range between 31o and 34o is similar to the surface temperature of the skin and may not be noticeable. Pain from coldness and heat is perceived at temperatures of about &lt;12 oC and &gt;45 oC, respectively.

Thermosensation and Transient Receptor Potential

Peripheral thermosensation is the perception of external temperature. A change in temperature (on the surface of the skin and other tissues) is detected ...