This work was supported by the China National Major Scientific Instruments Development Project (Grant No. 51427804) and the Shandong Province National Natural Science Foundation (Grant No. ZR2017MEE023).

1. Sample preparation
<ol>
	<li>Collect raw coal blocks from the 4671B6 working face from the Xinzhuangzi coal mine. Note that, due to the low strength and looseness of the structure, the raw coal is broken and probably mixed with impurities. To avoid the influence of these internal and external factors, as well as reduce the inhomogeneity of coal as much as possible, select large coal blocks (about 15 cm long, 10 cm wide, and 10 cm high).</li>
	<li>Use a tweezer to remove impurities mixed in the coal and scrub the crusher chamber with absorbent cotton and acetaldehyde.</li>
	<li>Smash the coal blocks into small pieces with a jaw crusher, and shelter them in a sieve shaker equipped with standard screens of 6 and 16 mesh. Place the sorted coal powder separately according to diameter.</li>
	<li>Weigh 1,000 g and 300 g of pulverized coal with a particle size distribution of 0&#8211;1 mm and 1&#8211; 3 mm, respectively. Put them together in a beaker in a mass proportion of 0.76:0.24 and mix them well with a glass rod (with a diameter of 6 mm). 
	NOTE: According to the Gaudian-Schuman function of continuous packing theory, when the particle size distribution value (m) equals approximately 0.25 (mass of particle size is 1&#8211;3 mm: total mass = 0.24), the strength of the briquette is maximal30.</li>
	<li>To prepare the cement, put 4 g of sodium humate powder (99.99% purity) into a beaker and add approximately 96 mL of distilled water. Use a glass rod to stir them and make sure that all sodium humate is well dissolved. 
	NOTE: The concentration of cement directly affects the compressive strength of briquette. Table 1 reveals specific ratios of briquette preparation, of which the No. 2 sample has been used for the representative results.</li>
	<li>Put 230 g of mixed coal powder and 20 g of sodium humate solution into a beaker and mix them together. 
	NOTE: Based on previous experiences of making samples, a briquette produced with 250 g of material, using the cold press method, meets the size requirement of a standard rock sample22, where coal powder accounts for 92% and cement accounts for 8%.</li>
	<li>Cold-press the briquette using the shaping tools adapted to the size of the briquette (Figure 3).
	<ol>
		<li>To produce a standard-sized briquette, coat the inner surface of the shaping tools with lubricating oil. Assemble tool components #2, #3, and #4 of Figure 3, and fill the hole with 250 g of mixed material.</li>
		<li>Put component #1 of Figure 3 on top of the material, and place everything under the piston of an electro-hydraulic servo universal testing machine.</li>
		<li>Launch the software WinWdw (or equivalent) to control the electro-hydraulic servo universal testing machine. In the software, click on Force Range to set the maximum force to 50 kN, and click on Reset to clear the displacement value.</li>
		<li>Left-click on the option force loading control. Set the moving ratio at 0.1 kN/s. Set the target force value at 29.4 kN and holding time at 900 s. Then, click on Start.</li>
		<li>Take out the shaping tools and invert them onto a rubber plate. Use a rubber hammer to disassemble tool components #4, #2, #3, and #1 in that order.</li>
	</ol>
	</li>
	<li>Put the briquette in a 40 &#176;C incubator for 48 h. Then, weigh its mass with electronic scales (with a precision of 0.01 g) and measure its height and diameter with a Vernier caliper (with a precision of 0.02 mm) after drying.</li>
	<li>Measure the moisture content, ash content, and volatile content of the briquette, using a proximate analyzer (see the Table of Materials) at a temperature of 20 &#176;C and a relative humidity of 65% (per standard GB/T 212-2008). Perform a vitrinite reflectance measurement on the polished briquette, using a photometer microscope (per standard GB/T 6948-2008).</li>
	<li>Measure the uniaxial compressive strength, tensile strength, cohesion, and internal friction angle, using a universal testing machine and a strain controlled direct shear apparatus (per standard GB/T 23561-2010). Perform a Poisson ratio measurement using a resistance strain gauge (per standard GB/T 22315-2008).</li>
	<li>Conduct an adsorption test of the raw coal and the briquette, using an isotherm adsorption instrument (per standard GB/T19560-2008).</li>
</ol>
2. Experimental methods
<ol>
	<li>Laboratory setup
	<ol>
		<li>Place the test system in a quiet, vibration-free area of a clean laboratory without electromagnetic interference. The room temperature should remain stable during the test.</li>
		<li>Put the visualized vessel on the platform of the electro-hydraulic servo universal testing machine. Connect the piston of the testing machine with that of the visualized vessel with the use of a specific tool (see Figure 4).</li>
		<li>Install a manual pressure-reducing valve in the gas tank nozzle. Connect the valve with the gas filling channel at the bottom plate of the visualized vessel by soft pipe (with an inner diameter of 5 mm and a maximal pressure of 30 MPa). Link the vacuum channel and the vacuum pump with the same pipe.</li>
		<li>Fix the back door of the visualized vessel with high-strength bolts. Connect the computer, data acquisition box (DAQ box), and the embedded gas pressure sensor to the back door.</li>
	</ol>
	</li>
	<li>Air tightness test and blank measurement
	<ol>
		<li>To acquire the gas pressure data in the visualized vessel, launch the software DAQ Sensor-16 (or equivalent). On the software, click on Start.</li>
		<li>Start the vacuum pump. Open the valve V1 (Figure 2) and close V2, V3, and V4 (Figure 2). Vacuum the visualized vessel chamber. Turn off V1 and vacuum-pump it until it is under vacuum.</li>
		<li>Open V2 and the gas tank (with helium). Use the manual pressure-reducing valve to adjust the outlet pressure of the gas tank to approximate 2 MPa (relative pressure).</li>
		<li>Carefully observe the gas pressure curve displayed on DAQ Sensor-16. When it is about 2 MPa, turn off V2 and the gas tank. 
		NOTE: After 24 h, if the reduction of the gas pressure is less than 5%, the sealability of the visualized vessel is good.</li>
		<li>To measure the friction force of the loading piston moving downward, launch the software WinWdw to control the electro-hydraulic servo universal testing machine.</li>
		<li>In the software, click on Force Range to set the maximum force to 5 kN and click on Reset to clear the displacement value. Left-click on the option Displacement Loading Rate. Set the moving ratio at 1 mm/min; then, click on Start.</li>
		<li>When the displacement displayed on WinWdw is approximately 5 mm, click on Stop. Left-click on Data Save to save the force-displacement curve.</li>
		<li>Open V4 and discharge helium into air. Disassemble the back door of the visualized vessel and close V4. 
		CAUTION: The door and windows should be open for ventilation during the gas release due to the possible suffocation hazard.</li>
	</ol>
	</li>
	<li>Uniaxial compression experiment
	<ol>
		<li>Measure the height (h) and diameter (d) of the briquette with a Vernier caliper (with a precision of 0.02 mm). Weigh the mass (m) of the briquette with electronic scales (with a precision of 0.01 g). Calculate its apparent density (<img alt="Equation 1" src="/files/ftp_upload/59405/59405eq1.jpg" />) with the following equation. 
		&#8203;<img alt="Equation 2" src="/files/ftp_upload/59405/59405eq2.jpg" /></li>
		<li>Install the chain roller of the circumferential deformation test apparatus around the middle position of the briquette (Figure 5, #1) and fix the clamp holder (Figure 5, #2). Connect the sensor (Figure 5, #3) with the DAQ box through the aviation connector in the visualized vessel (Figure 2) and place them under the loading piston. 
		NOTE: To ensure the accuracy of the data acquisition, adjust the chain roller and the top surface of the sample so that they are parallel to the loading piston.</li>
		<li>Launch WinWdw to control the universal testing machine. In the software, left-click on the option Displacement Loading Rate. Set the moving ratio at 10 mm/min. Press the Down button on the remote controller of the universal testing machine until the distance left between the piston and the sample is 1&#8211;2 mm. Then, assemble the back door of the visualized vessel.</li>
		<li>Repeat steps 2.2.1&#8211;2.2.2. Open V3 and the gas tank (CO2, purity = 99.99%). Use the manual pressure-reducing valve to adjust the outlet pressure of the gas tank to a certain value.</li>
		<li>Carefully observe the gas pressure curve displayed in DAQ Sensor-16. When it gets close enough to the target value, close V3 and the gas tank (CO2). 
		NOTE: When the gas pressure curve remains stable, the briquette has reached its adsorption and desorption dynamic equilibrium state. Generally, it takes 6&#8211;8 h for the briquette to fully adsorb. In this test, the adsorption time is set at 24 h.</li>
		<li>After 24 h, place the camera with a tripod beside the window of the visualized vessel. Adjust the height and angle to ensure that the image of the sample is shown in the center of the camera screen.</li>
		<li>Start the software SDU deformation acquisition V2.0 (or equivalent) to monitor the circumferential deformation of the briquette. Click on Start.</li>
		<li>On WinWdw, click on New Sample and type in the height and diameter of the briquette, click on Sectional Area, and then click on Confirm. Click on Force Range to set the maximum force to 5 kN, and click on Reset to clear the displacement value.</li>
		<li>Left-click on the option Displacement Loading Rate and set the moving ratio at 1 mm/min. Click on Start to compress the sample. At the same time, press the Start button on the camera to begin video recording.</li>
		<li>When the sample totally fails, click on Stop and Data Save, in that order, in both WinWdw and SDU deformation acquisition V2.0. Press the Start button again on the camera to stop video recording.</li>
		<li>Repeat step 2.2.8 to release CO2 in the vessel chamber. Disconnect the aviation connectors for the gas pressure sensor and circumferential deformation test apparatus.</li>
		<li>Left-click on the option Displacement Loading Rate on WinWdw. Set the moving ratio at 10 mm/min. Press the Up button on the remote controller of the universal testing machine. When the loading piston of the vessel is around 2&#8211;3 mm above the briquette, take the briquette out and remove it from the chain roller.</li>
		<li>Dismantle the connecting tool between the pistons. Clean the visualized vessel with a vacuum cleaner.</li>
	</ol>
	</li>
	<li>Completion
	<ol>
		<li>Based on the stress-axial strain curve and circumferential strain curve obtained from WinWdw and SDU deformation acquisition V2.0, calculate the volume strain of the sample with the following equation. 
		<img alt="Equation 3" src="/files/ftp_upload/59405/59405eq3.jpg" /> 
		&#8203;Here, <img alt="Equation 4" src="/files/ftp_upload/59405/59405eq4.jpg" /> = volume strain; <img alt="Equation 5" src="/files/ftp_upload/59405/59405eq5.jpg" /> = axial strain; <img alt="Equation 6" src="/files/ftp_upload/59405/59405eq6.jpg" /> = circumferential strain.</li>
		<li>Obtain the peak strength from the stress-axial strain curve. The strength reduction rate is calculated as follows. 
		<img alt="Equation 7" src="/files/ftp_upload/59405/59405eq7.jpg" /> 
		&#8203;Here, <img alt="Equation 8" src="/files/ftp_upload/59405/59405eq8.jpg" /> = strength reduction rate; <img alt="Equation 9" src="/files/ftp_upload/59405/59405eq9.jpg" /> = peak strength of the sample under a different pressure of CO2; <img alt="Equation 10" src="/files/ftp_upload/59405/59405eq10.jpg" /> = peak strength of the sample in atmospheric air.</li>
		<li>Calculate the elastic modulus using the linear stage in the stress-axial strain curve according to the following equation. 
		<img alt="Equation 11" src="/files/ftp_upload/59405/59405eq11.jpg" /> 
		Here, <img alt="Equation 12" src="/files/ftp_upload/59405/59405eq12.jpg" /> = elastic modulus of the sample; <img alt="Equation 13" src="/files/ftp_upload/59405/59405eq13.jpg" /> = stress increment of linear the stage (in megapascal); <img alt="Equation 14" src="/files/ftp_upload/59405/59405eq14.jpg" /> = strain increment of the linear stage. Calculate the elastic modulus reduction rate as follows. 
		<img alt="Equation 15" src="/files/ftp_upload/59405/59405eq15.jpg" /> 
		&#8203;Here, <img alt="Equation 16" src="/files/ftp_upload/59405/59405eq16.jpg" /> = elastic modulus reduction rate, <img alt="Equation 12" src="/files/ftp_upload/59405/59405eq12.jpg" /> = elastic modulus of the sample under a different pressure of CO2; <img alt="Equation 17" src="/files/ftp_upload/59405/59405eq17.jpg" /> = elastic modulus of the sample in atmospheric air.</li>
		<li>Select sample photos during the test and statistics fracture covering area using a program (e.g., written in MATLAB) according to the box-counting dimension method. 
		<img alt="Equation 18" src="/files/ftp_upload/59405/59405eq18.jpg" /> 
		&#8203;Here, <img alt="Equation 19" src="/files/ftp_upload/59405/59405eq19.jpg" /> = grid number to cover the fracture area at the square grid side length of <img alt="Equation 20" src="/files/ftp_upload/59405/59405eq20.jpg" />; <img alt="Equation 21" src="/files/ftp_upload/59405/59405eq21.jpg" /> = a constant; <img alt="Equation 22" src="/files/ftp_upload/59405/59405eq22.jpg" /> = fractal dimension; <img alt="Equation 20" src="/files/ftp_upload/59405/59405eq20.jpg" /> = side length of the square grid. The minimum grid size equals the pixel size in this test.
		<ol>
			<li>Calculate the correlation coefficient according to the following equation. 
			<img alt="Equation 23" src="/files/ftp_upload/59405/59405eq23.jpg" /> 
			Here,<img alt="Equation 24" src="/files/ftp_upload/59405/59405eq24.jpg" /> = correlation coefficient; <img alt="Equation 25" src="/files/ftp_upload/59405/59405eq25.jpg" /> = covariance of <img alt="Equation 26" src="/files/ftp_upload/59405/59405eq26.jpg" /> and <img alt="Equation 27" src="/files/ftp_upload/59405/59405eq27.jpg" />; <img alt="Equation 28" src="/files/ftp_upload/59405/59405eq28.jpg" /> = variance of <img alt="Equation 26" src="/files/ftp_upload/59405/59405eq26.jpg" />; <img alt="Equation 29" src="/files/ftp_upload/59405/59405eq29.jpg" /> = variance of <img alt="Equation 27" src="/files/ftp_upload/59405/59405eq27.jpg" />.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

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C., 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=Development+and+application+of+a+gas-solid+coupling+test+system+in+the+visualized+and+constant+volume+loading+state.">Development and application of a gas-solid coupling test system in the visualized and constant volume loading state.</a> Journal of China University of Mining &amp; Technology. 47 (1), 104-112 (2018).</li><li>Allen, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Particle Size Measure. , (1984).</li><li>Wang, H. 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Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Study on density and refractive index of near-critical fluid. , (2009).</li><li>Ruppel, T. C., Grein, C. T., Bienstock, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adsorption+of+methane+on+dry+coal+at+elevated+pressure.">Adsorption of methane on dry coal at elevated pressure.</a> Fuel. 53 (3), 152-162 (1974).</li><li>Ranjith, P. G., Jasinge, D., Choi, S. K., Mehic, M., Shannon, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+CO2+saturation+on+mechanical+properties+of+Australian+black+coal+using+acoustic+emission.">The effect of CO2 saturation on mechanical properties of Australian black coal using acoustic emission.</a> Fuel. 89 (8), 2110-2117 (2010).</li><li>Viete, D. R., Ranjith, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+CO2,+on+the+geomechanical+and+permeability+behaviour+of+brown+coal:+Implications+for+coal+seam+CO2+sequestration.">The effect of CO2, on the geomechanical and permeability behaviour of brown coal: Implications for coal seam CO2 sequestration.</a> International Journal of Coal Geology. 66 (3), 204-216 (2006).</li><li>Jiang, Y. D., Zhu, J., Zhao, Y. X., Liu, J. H., Wang, H. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Constitutive+equations+of+coal+containing+methane+based+on+mixture+theory.">Constitutive equations of coal containing methane based on mixture theory.</a> Journal of China Coal Society. 32 (11), 1132-1137 (2007).</li><li>Xie, H. P., Gao, F., Zhou, H. W., Zuo, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fractal+fracture+and+fragmentation+in+rocks.">Fractal fracture and fragmentation in rocks.</a> Journal of Seismology. 23 (4), 1-9 (2003).</li><li>Miao, T. J., Yu, B. M., Duan, Y. G., Fang, Q. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+fractal+analysis+of+permeability+for+fractured+rocks.">A fractal analysis of permeability for fractured rocks.</a> International Journal of Heat &amp; Mass Transfer. 81 (81), 75-80 (2015).</li><li>Liu, R. C., Jiang, Y. J., Li, B., Wang, X. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+fractal+model+for+characterizing+fluid+flow+in+fractured+rock+masses+based+on+randomly+distributed+rock+fracture+networks.">A fractal model for characterizing fluid flow in fractured rock masses based on randomly distributed rock fracture networks.</a> Computers &amp; Geotechnics. 65, 45-55 (2015).</li><li>Pan, J. N., 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=Micro-pores+and+fractures+of+coals+analysed+by+field+emission+scanning+electron+microscopy+and+fractal+theory.">Micro-pores and fractures of coals analysed by field emission scanning electron microscopy and fractal theory.</a> Fuel. 164, 277-285 (2016).</li></ol>

The authors have nothing to disclose.

Considering the danger of high-pressure gas, some critical steps are important during the test. The valves and O rings should be inspected and replaced regularly, and any source of ignition should not be allowed in the laboratory. When using the manual pressure-regulating valve, the experimenter should twist the valve slowly to make the pressure in the visualized vessel increase gradually. Do not disassemble the vessel during the test. When the experiment is finished, the back door of the vessel should be opened after th...

The increasing concentration of CO2 in the atmosphere is a direct factor causing the global warming effect. Due to the strong sorption capacity of coal, CO2 sequestration in a coal seam is regarded as a practical and environment-friendly means to reduce the global emission of greenhouse gas1,2,3. At the same time, the injected CO2 can replace CH4 and result in gas production promotion in coalbed methane recovery (ECBM)4,5,6. The ecological and economic prospects of CO2 sequestration have recently attracted worldwide attention among researchers, as well as among different international environmental protection groups and governmental agencies.
Coal is a heterogeneous, structurally anisotropic rock composed of a pore, fracture, and coal matrix. The pore structure&#160;has a large specific surface area, which can adsorb a large amount of gas, playing a vital role in gas sequestration, and the fracture is the main path for free gas flow7,8. This unique physical structure leads to a great gas adsorption capacity for CH4 and CO2. Mine gas is deposited in coalbed in a few forms: (1) adsorbed on the surface of micropores and larger pores; (2) absorbed in the coal molecular structure; (3) as free gas in fractures and larger pores; and (4) dissolved in deposit water. The sorption behavior of coal to CH4 and CO2 causes matrix swelling, and further studies demonstrate that it is a heterogeneous process and is related to the coal lithotypes9,10,11. In addition, gas sorption can result in damage in the constitutive relation of coal12,13,14.
The raw coal sample is generally used in coal and CO2 coupling experiments. Specifically, a large piece of raw coal from the working face in a coal mine is cut to prepare a sample. However, the physical and mechanical properties of raw coal inevitably have a high dispersion degree due to the random spatial distribution of natural pores and fractures in a coal seam. Moreover, the gas-bearing coal is soft and difficult to be reshaped. According to the principles of the orthogonal experimental method, the briquette, which is reconstituted with raw coal powder and cement, is regarded as an ideal material used in the coal sorption test15,16. Being cold-pressed with metal dies, its strength can be preset and remains stable by adjusting the quantity of cement, which benefits the comparative analysis of the single-variable effect. Additionally, although the porosity of the briquette sample is ~4-10 times, that of the raw coal sample, similar adsorption and desorption characteristics and stress-strain curve have been found in the experimental research17,18,19,20. In this paper, a scheme of a similar material for gas-bearing coal has been adopted to prepare the briquette21. The raw coal was taken from the 4671B6 working face in the Xinzhuangzi Coal Mine, Huainan, Anhui Province, China. The coal seam is approximately 450 m below ground level and 360 m below sea level, and it dips at about 15&#176; and is approximately 1.6 m in thickness. The height and diameter of the briquette sample are 100 mm and 50 mm, respectively, which is the recommended size suggested by the International Society for Rock Mechanics (ISRM)22.
The previous uniaxial or triaxial loading test instruments for gas-bearing coal experiments under laboratory conditions have some shortages and limitations, presented as fellows23,24,25,26,27,28: (1) during the loading process, the vessel volume decreases with the piston moving, causing fluctuations in gas pressure and disturbances in gas sorption; (2) the real-time image monitoring of samples, as well as circumferential deformation measurements in a high gas pressure environment, is difficult to conduct; (3) they are limited to stimulation of dynamic load disturbances on preloaded samples to analyze their mechanical response characteristics. In order to improve the instrument precision and data acquisition in the gas-solid coupling condition, a visualized and constant-volume test system29 has been developed (Figure 1), including (1) a visualized loading vessel with a constant volume chamber, which is the core component; (2) a gas filling module with a vacuum channel, two filling channels, and a releasing channel; (3) an axial loading module consisting of an electro-hydraulic servo universal testing machine and control computer; (4) a data acquisition module comprised of a circumferential displacement measurement apparatus, a gas pressure sensor, and a camera at the window of the visualized loading vessel.
The core visualized vessel (Figure 2) is specifically designed so that two adjusting cylinders are fixed on the upper plate and their pistons move simultaneously with the loading one through a beam, and the sectional area of the loading piston is equal to the sum of that of the adjusting cylinders. Flowing through an inner hole and soft pipes, the high-pressure gas in the vessel and the two cylinders is connected. Therefore, when the vessel-loading piston moves downward and compresses the gas, this structure can offset the change in volume and eliminate pressure interference. In addition, the enormous gas-induced counterforce exerting on the piston is prevented during the test, significantly improving the safety of the instrument. The windows, which are equipped with tempered borosilicate glass and situated on three sides of the vessel, provide a direct way to take a photograph of the sample. This glass has been successfully tested and proved to resist up to 10 MPa gas with a low expansion rate, high strength, light transmittance, and chemical stability29.
This paper describes the procedure to perform a uniaxial compression experiment of CO2-bearing coal with the new visualized and constant-volume gas-solid coupling test system, which includes the description of all pieces that prepare a briquette sample using raw coal powder and sodium humate, as well as the successive steps to inject high-pressure CO2 and conduct uniaxial compression. The whole sample deformation process is monitored using a camera. This experimental approach offers an alternative way to quantitively analyze the adsorption-induced damage and fracture evolution characteristic of gas-bearing coal.

<table>
	<tbody>
		<tr>
			<td>3Y-Leica MPV-SP photometer microphotometric system</td>
			<td>Leica,Germany</td>
			<td>M090063016</td>
			<td>Used for vitrinite 
			reflectance measurement</td>
		</tr>
		<tr>
			<td>Automatic isotherm adsorption instrument</td>
			<td>BeiShiDe Instrument Technology (Beijing)CO.,Ltd.</td>
			<td>3H-2000PH</td>
			<td>Isothermal adsorption test</td>
		</tr>
		<tr>
			<td>Electro hydraulic servo universal testing machine</td>
			<td>Jinan Shidaishijin testing machine CO.,Ltd</td>
			<td>WDW-100EIII</td>
			<td>Used to provide 
			axial pressure</td>
		</tr>
		<tr>
			<td>Gas pressure sensor</td>
			<td>Beijing Star Sensor Technology CO.,LTD</td>
			<td>CYYZ11</td>
			<td>Gas pressure monitoring</td>
		</tr>
		<tr>
			<td>Gas tank(carbon dioxide/helium)</td>
			<td>Heifei Henglong Gas.,Ltd</td>
			<td></td>
			<td>Gas resource</td>
		</tr>
		<tr>
			<td>high-speed camera</td>
			<td>Sony corporation</td>
			<td>FDR-AX30</td>
			<td>Image monitoring</td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Yuyao YuanDong Digital Instrument Factory</td>
			<td>XGQ-2000</td>
			<td>Briquette drying</td>
		</tr>
		<tr>
			<td>jaw crusher</td>
			<td>Hebi Tianke Instrument CO.,Ltd</td>
			<td>EP-2</td>
			<td>Coal grinding</td>
		</tr>
		<tr>
			<td>Manual pressure reducing valve</td>
			<td>Shanghai Saergen Instrument CO.,Ltd</td>
			<td>R41</td>
			<td>Outlet gas pressure adjustment</td>
		</tr>
		<tr>
			<td>Proximate Analyzer</td>
			<td>Changsha Kaiyuan Instrument CO.,Ltd</td>
			<td>5E-MAG6700</td>
			<td>Coal industrial analysis</td>
		</tr>
		<tr>
			<td>Resistance strain gauge</td>
			<td>Jinan Sigmar Technology CO.,LTD</td>
			<td>ASMB3-16/8</td>
			<td>Poisson ratio measurement</td>
		</tr>
		<tr>
			<td>Sieve shaker (6,16mesh)</td>
			<td>Hebi Tianguan Instrument CO.,Ltd</td>
			<td>GZS-300</td>
			<td>Coal powder shelter</td>
		</tr>
		<tr>
			<td>Soft pipe</td>
			<td>Jinan Quanxing High pressure pipe CO.,Ltd</td>
			<td></td>
			<td>Inner diameter=5 mm 
			maximal pressure=30 MPa</td>
		</tr>
		<tr>
			<td>Standard rock sample circumferential deformation test apparatus</td>
			<td>Huainan Qingda Machinery CO.,Ltd</td>
			<td></td>
			<td>Circumferential deformation 
			acquisition</td>
		</tr>
		<tr>
			<td>Strain controlled 
			direct shear apparatus</td>
			<td>Beijing Aerospace Huayu Test Instrument CO.,LTD</td>
			<td>ZJ-4A</td>
			<td>Tensile strength, cohesion, internal friction 
			angle measurement</td>
		</tr>
		<tr>
			<td>Vaccum pump</td>
			<td>Fujiwara,Japan</td>
			<td>750D</td>
			<td>Used to vaccumize the vessel</td>
		</tr>
		<tr>
			<td>Valve</td>
			<td>Jiangsu Subei Valve Co.,Ltd</td>
			<td>S4 NS-MG16-MF1</td>
			<td>Gas seal</td>
		</tr>
		<tr>
			<td>Visual loading vessel</td>
			<td>Huainan Qingda Machinery CO.,Ltd</td>
			<td></td>
			<td>Instrument for sample 
			loading and real-time monitoring</td>
		</tr>
	</tbody>
</table>

a uniaxial compression experiment with co2-bearing coal using a visualized and constant-volume gas-solid coupling test system

Injecting carbon dioxide (CO2) into a deep coal seam is of great significance for reducing the concentration of greenhouse gases in the atmosphere and increasing the recovery of coalbed methane. A visualized and constant-volume gas-solid coupling system is introduced here to investigate the influence of CO2 sorption on the physical and mechanical properties of coal. Being able to keep a constant volume and monitor the sample using a camera, this system offers the potential to improve instrument accuracy and analyze fracture evolution with a fractal geometry method. This paper provides all steps to perform a uniaxial compression experiment with a briquette sample in different CO2 pressures with the gas-solid coupling test system. A briquette, cold-pressed by raw coal and sodium humate cement, is loaded in high-pressure CO2, and its surface is monitored in real-time using a camera. However, the similarity between the briquette and the raw coal still needs improvement, and a flammable gas such as methane (CH4) cannot be injected for the test. The results show that CO2 sorption leads to peak strength and elastic modulus reduction of the briquette, and the fracture evolution of the briquette in a failure state indicates fractal characteristics. The strength, elastic modulus, and fractal dimension are all correlated with CO2 pressure but not with a linear correlation. The visualized and constant-volume gas-solid coupling test system can serve as a platform for experimental research about rock mechanics considering the multifield coupling effect.

The average mass of the briquette sample was 230 g. Depending on the industrial analysis, the briquette exhibited a moisture content of 4.52% and an ash content of 15.52%. Furthermore, the volatile content was approximately 31.24%. As the sodium humate was extracted from the coal, the components of the briquette were similar to raw coal. The physical characteristics are displayed in Table 2.
The comparison of th...

Watch this Scientific Journal Video about A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System at JoVE.com

A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System

This protocol demonstrates how to prepare a briquette sample and conduct a uniaxial compression experiment with a briquette in different CO2 pressures using a visualized and constant-volume gas-solid coupling test system. It also aims to investigate changes in terms of coal&#8217;s physical and mechanical properties induced by CO2 adsorption.

A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System

Injecting carbon dioxide (CO2) into a deep coal seam is of great significance for reducing the concentration of greenhouse gases in the atmosphere and ...

a-uniaxial-compression-experiment-with-co2-bearing-coal-using

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8.6K Views.  Shandong University. This protocol demonstrates how to prepare a briquette sample and conduct a uniaxial compression experiment with a briquette in different CO2 pressures using a visualized and constant-volume gas-solid coupling test system. It also aims to investigate changes in terms of coal’s physical and mechanical properties induced by CO2 adsorption.

Video: A Uniaxial Compression Experiment with CO2-Bearing Coal Using a Visualized and Constant-Volume Gas-Solid Coupling Test System

A Bending Test for Determining the Atterberg Plastic Limit in Soils

The thread rolling test is the most commonly used method to determine the plastic limit (PL) in soils. It has been widely criticized, because a considerable subjective judgment from the operator that carries out the test is involved during its performance, which may affect the final result significantly. Different alternative methods have been put forward, but they cannot compete with the standard rolling test in speed, simplicity and cost.
In an earlier study by the authors, a simple method with a simple device to determine the PL was presented (the &#34;thread bending test&#34; or simply &#34;bending test&#34;); this method allowed the PL to be obtained with minimal operator interference. In the present paper a version of the original bending test is shown. The experimental basis is the same as the original bending test: soil threads which are 3 mm in diameter and 52 mm long are bent until they start to crack, so that both the bending produced and its related moisture content are determined. However, this new version enables the calculation of PL from an equation, so it is not necessary to plot any curve or straight line to obtain this parameter and, in fact, the PL can be achieved with only one experimental point (but two experimental points are recommended).
The PL results obtained with this new version are very similar to those obtained through the original bending test and the standard rolling test by a highly experienced operator. Only in particular cases of high plasticity cohesive soils, there is a greater difference in the result. Despite this, the bending test works very well for all types of soil, both cohesive and very low plasticity soils, where the latter are the most difficult to test via the standard thread rolling method.

The traditional standardized test for determining the plastic limit in soils is performed by hand, and the result varies depending on the operator. An alternative method based on bending measurements is presented in this study. This allows the plastic limit to be obtained with a clear and objective criterion.

The thread rolling test is the most commonly used method to determine the plastic limit (PL) in soils. It has been widely criticized, because a ...

Measuring and Mapping Patterns of Soil Erosion and Deposition Related to Soil Carbonate Concentrations Under Agricultural Management

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonate (CaCO3) profiles. The objective is to describe a simple conceptual model and detailed protocol for repeatable field and laboratory measurements of these quantities. Here, accurate elevation is measured using a ground-based differential global positioning system (GPS); other data acquisition methods could be applied to the same basic method. Soil samples are collected from prescribed depth intervals and analyzed in the lab using an efficient and precise modified pressure-calcimeter method for quantitative analysis of inorganic carbon concentration. Standard statistical methods are applied to point data, and representative results show significant correlations between changes in soil surface layer CaCO3 and changes in elevation consistent with the conceptual model; CaCO3 generally decreased in depositional areas and increased in erosional areas. Maps are derived from point measurements of elevation and soil CaCO3 to aid analyses. A map of erosional and depositional patterns at the study site, a rain-fed winter wheat field cropped in alternating wheat-fallow strips, shows the interacting effects of water and wind erosion affected by management and topography. Alternative sampling methods and depth intervals are discussed and recommended for future work relating soil erosion and deposition to soil CaCO3.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes in elevation are related to changes in near-surface soil carbonates. Repeatable methods for field and laboratory measurements of these quantities and data analysis methods are described here.

Spatial patterns of soil erosion and deposition can be inferred from differences in ground elevation mapped at appropriate time increments. Such changes ...

Techniques for Investigating the Anatomy of the Ant Visual System

This article outlines a suite of techniques in light microscopy (LM) and electron microscopy (EM) which can be used to study the internal and external eye anatomy of insects. These include traditional histological techniques optimized for work on ant eyes and adapted to work in concert with other techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). These techniques, although vastly useful, can be difficult for the novice microscopist, so great emphasis has been placed in this article on troubleshooting and optimization for different specimens. We provide information on imaging techniques for the entire specimen (photo-microscopy and SEM) and discuss their advantages and disadvantages. We highlight the technique used in determining lens diameters for the entire eye and discuss new techniques for improvement. Lastly, we discuss techniques involved in preparing samples for LM and TEM, sectioning, staining, and imaging these samples. We discuss the hurdles that one might come across when preparing samples and how best to navigate around them.

This article outlines a suite of techniques in light and electron microscopy to study the internal and external eye anatomy of insects. These include several traditional techniques optimized for work on ant eyes, detailed troubleshooting, and suggestions for optimization for different specimens and regions of interest.

This article outlines a suite of techniques in light microscopy (LM) and electron microscopy (EM) which can be used to study the internal and external eye ...

On-Site Molecular Detection of Soil-Borne Phytopathogens Using a Portable Real-Time PCR System

On-site diagnosis of plant diseases can be a useful tool for growers for timely decisions enabling the earlier implementation of disease management strategies that reduce the impact of the disease. Presently in many diagnostic laboratories, the polymerase chain reaction (PCR), particularly real-time PCR, is considered the most sensitive and accurate method for plant pathogen detection. However, laboratory-based PCRs typically require expensive laboratory equipment and skilled personnel. In this study, soil-borne pathogens of potato are used to demonstrate the potential for on-site molecular detection. This was achieved using a rapid and simple protocol comprising of magnetic bead-based nucleic acid extraction, portable real-time PCR (fluorogenic probe-based assay). The portable real-time PCR approach compared favorably with a laboratory-based system, detecting as few as 100 copies of DNA from Spongospora subterranea. The portable real-time PCR method developed here can serve as an alternative to laboratory-based approaches and a useful on-site tool for pathogen diagnosis.

Rapid and accurate detection of plant pathogens on-site, especially soil-borne pathogens, is crucial to prevent further inoculum production and proliferation of plant diseases in the field. The method developed here using a portable real-time PCR detection system enables on-site diagnosis under field conditions.

On-site diagnosis of plant diseases can be a useful tool for growers for timely decisions enabling the earlier implementation of disease management ...

Stress Distribution During Cold Compression of Rocks and Mineral Aggregates Using Synchrotron-based X-Ray Diffraction

We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) coupled with synchrotron X-radiation. A cube-shaped sample assembly is prepared and compressed, at room temperature, by a set of four X-ray transparent sintered diamond anvils and two tungsten carbide anvils, in the lateral and the vertical planes, respectively. All six anvils are housed within a 250-ton hydraulic press and driven inward simultaneously by two wedged guide blocks. A horizontal energy dispersive X-ray beam is projected through and diffracted by the sample assembly. The beam is commonly in the mode of either white or monochromatic X-ray. In the case of white X-ray, the diffracted X-rays are detected by a solid-state detector array that collects the resulting energy dispersive diffraction pattern. In the case of monochromatic X-ray, the diffracted pattern is recorded using a two-dimensional (2-D) detector, such as an imaging plate or a charge-coupled device (CCD) detector. The 2-D diffraction patterns are analyzed to derive lattice spacings. The elastic strains of the sample are derived from the atomic lattice spacing within grains. The stress is then calculated using the predetermined elastic modulus and the elastic strain. Furthermore, the stress distribution in two-dimensions allow for understanding how stress is distributed in different orientations. In addition, a scintillator in the X-ray path yields a visible light image of the sample environment, which allows for the precise measurement of sample length changes during the experiment, yielding a direct measurement of volume strain on the sample. This type of experiment can quantify the stress distribution within geomaterials, which can ultimately shed light on the mechanism responsible for compaction. Such knowledge has the potential to significantly improve our understanding of key processes in rock mechanics, geotechnical engineering, mineral physics, and material science applications where compactive processes are important.

We report detailed procedures for compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus coupled with synchrotron X-radiation. Such experiments allow quantification of the stress distribution within samples, that ultimately sheds light on compaction processes in geomaterials.

We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) ...

Sampling, Sorting, and Characterizing Microplastics in Aquatic Environments with High Suspended Sediment Loads and Large Floating Debris

The ubiquitous presence of plastic debris in the ocean is widely recognized by the public, scientific communities, and government agencies. However, only recently have microplastics in freshwater systems, such as rivers and lakes, been quantified. Microplastic sampling at the surface usually consists of deploying drift nets behind either a stationary or moving boat, which limits the sampling to environments with low levels of suspended sediments and floating or submerged debris. Previous studies that employed drift nets to collect microplastic debris typically used nets with &#8805;300 &#181;m mesh size, allowing plastic debris (particles and fibers) below this size to pass through the net and elude quantification. The protocol detailed here enables: 1) sample collection in environments with high suspended loads and floating or submerged debris and 2) the capture and quantification of microplastic particles and fibers &lt;300 &#181;m. Water samples were collected using a peristaltic pump in low-density polyethylene (PE) containers to be stored before filtering and analysis in the lab. Filtration was done with a custom-made microplastic filtration device containing detachable union joints that housed nylon mesh sieves and mixed cellulose ester membrane filters. Mesh sieves and membrane filters were examined with a stereomicroscope to quantify and separate microplastic particulates and fibers. These materials were then examined using a micro-attenuated total reflectance Fourier transform infrared spectrometer (micro ATR-FTIR) to determine microplastic polymer type. Recovery was measured by spiking samples using blue PE particulates and green nylon fibers; percent recovery was determined to be 100% for particulates and 92% for fibers. This protocol will guide similar studies on microplastics in high velocity rivers with high concentrations of sediment. With simple modifications to the peristaltic pump and filtration device, users can collect and analyze various sample volumes and particulate sizes.

Most microplastic research to date has occurred in marine systems where suspended solid levels are relatively low. Focus is now shifting to freshwater systems, which may feature high sediment loads and floating debris. This protocol addresses collecting and analyzing microplastic samples from aquatic environments that contain high suspended solid loads.

The ubiquitous presence of plastic debris in the ocean is widely recognized by the public, scientific communities, and government agencies. However, only ...

Measuring Stolons and Rhizomes of Turfgrasses Using a Digital Image Analysis System

Length and diameter of stolons or rhizomes are usually measured using simple rulers and calipers. This procedure is slow and laborious, so it is often used on a limited number of stolons or rhizomes. For this reason, these traits are limited in their use for morphological characterization of plants. The use of digital image analysis software technology may overcome measurement errors due to human mistakes, which tend to increase as the number and size of samples also increase. The protocol can be used for any kind of crop but is particularly suitable for forage or grasses, where plants are small and numerous. Turf samples consist of aboveground biomass and an upper soil layer to the depth of maximum rhizome development, depending on the species of interest. In studies, samples are washed from the soil, and stolons/rhizomes are cleaned by hand before analysis by digital image analysis software. The samples are further dried in a laboratory heating oven to measure dry weight; therefore, for each sample, the resultant data are total length, total dry weight, and average diameter. Scanned images can be corrected before analysis by excluding visible extraneous parts, such as remaining roots or leaves not removed with the cleaning process. Indeed, these fragments normally have much smaller diameters than stolons or rhizomes, so they can be easily excluded from analysis by fixing the minimum diameter below which objects are not considered. Stolon or rhizome density per unit area can then be calculated based on sample size. The advantage of this method is quick and efficient measurement of the length and average diameter of large sample numbers of stolons or rhizomes.

A software-based image analysis system provides an alternative method to study the morphology of stoloniferous and rhizomatous species. This protocol permits measurement of the length and diameter of stolons and rhizomes and can be applied to samples with a large amount of biomass and to a wide variety of species.

Length and diameter of stolons or rhizomes are usually measured using simple rulers and calipers. This procedure is slow and laborious, so it is often ...

Quantifying Plant Soluble Protein and Digestible Carbohydrate Content, Using Corn (Zea mays) As an Exemplar

Elemental data are commonly used to infer plant quality as a resource to herbivores. However, the ubiquity of carbon in biomolecules, the presence of nitrogen-containing plant defensive compounds, and variation in species-specific correlations between nitrogen and plant protein content all limit the accuracy of these inferences. Additionally, research focused on plant and/or herbivore physiology require a level of accuracy that is not achieved using generalized correlations. The methods presented here offer researchers a clear and rapid protocol for directly measuring plant soluble proteins and digestible carbohydrates, the two plant macronutrients most closely tied to animal physiological performance. The protocols combine well characterized colorimetric assays with optimized plant-specific digestion steps to provide precise and reproducible results. Our analyses of different sweet corn tissues show that these assays have the sensitivity to detect variation in plant soluble protein and digestible carbohydrate content across multiple spatial scales. These include between-plant differences across growing regions and plant species or varieties, as well as within-plant differences in tissue type and even positional differences within the same tissue. Combining soluble protein and digestible carbohydrate content with elemental data also has the potential to provide new opportunities in plant biology to connect plant mineral nutrition with plant physiological processes. These analyses also help generate the soluble protein and digestible carbohydrate data needed to study nutritional ecology, plant-herbivore interactions and food-web dynamics, which will in turn enhance physiology and ecological research.

Quantifying Plant Soluble Protein and Digestible Carbohydrate Content, Using Corn Zea mays As an Exemplar

The protocols described herein provide a clear and approachable methodology for measuring soluble protein and digestible (non-structural) carbohydrate content in plant tissues. The ability to quantify these two plant macronutrients has significant implications for advancing the fields of plant physiology, nutritional ecology, plant-herbivore interactions and food-web ecology.

Elemental data are commonly used to infer plant quality as a resource to herbivores. However, the ubiquity of carbon in biomolecules, the presence of ...

Xylem Water Distribution in Woody Plants Visualized with a Cryo-scanning Electron Microscope

A scanning electron microscope installed cryo-unit (cryo-SEM) allows specimen observation at subzero temperatures and has been used for exploring water distribution in plant tissues in combination with freeze fixation techniques using liquid nitrogen (LN2). For woody species, however, preparations for observing the xylem transverse-cut surface involve some difficulties due to the orientation of wood fibers. Additionally, higher tension in the water column in xylem conduits can occasionally cause artifactual changes in water distribution, especially during sample fixation and collection. In this study, we demonstrate an efficient procedure to observe the water distribution within the xylem of woody plants in situ&#160;by using a cryostat and cryo-SEM. At first, during sample collection, measuring the xylem water potential should determine whether high tension is present in the xylem conduits. When the xylem water potential is low (&#60; ca. &#8722;0.5 MPa), a tension relaxation procedure is needed to facilitate better preservation of the water status in xylem conduits during sample freeze fixation. Next, a watertight collar is attached around the tree stem and filled with LN2&#160;for freeze fixation of the water status of xylem. After harvesting, care should be taken to ensure that the sample is preserved frozen while completing the procedures of sample preparation for observation. A cryostat is employed to clearly expose the xylem transverse-cut surface. In cryo-SEM observations, time adjustment for freeze-etching is required to remove frost dust and accentuate the edge of the cell walls on the viewing surface. Our results demonstrate the applicability of cryo-SEM techniques for the observation of water distribution within xylem at cellular and subcellular levels. The combination of cryo-SEM with non-destructive in situ observation techniques will profoundly improve the exploration of woody plant water flow dynamics.

Observing the water distribution within the xylem provides significant information regarding water flow dynamics in woody plants. In this study, we demonstrate the practical approach to observe xylem water distribution in situ&#160;by using a cryostat and cryo-SEM, which eliminates artifactual changes in the water status during sample preparation.

A scanning electron microscope installed cryo-unit (cryo-SEM) allows specimen observation at subzero temperatures and has been used for exploring water ...

Removal of Arsenic Using a Cationic Polymer Gel Impregnated with Iron Hydroxide

In this work, we prepared an adsorbent composed of a cationic polymer gel containing iron hydroxide in its structure designed to adsorb arsenic from groundwater. The gel we selected was the N,N-dimethylamino propylacrylamide methyl chloride quaternary (DMAPAAQ) gel. The objective of our preparation method was to ensure the maximum content of iron hydroxide in the structure of the gel. This design approach enabled simultaneous adsorption by both the polymer structure of the gel and the iron hydroxide component, thus, enhancing the adsorption capacity of the material. To examine the performance of the gel, we measured reaction kinetics, carried out pH sensitivity and selectivity analyses, monitored arsenic adsorption performance, and conducted regeneration experiments. We determined that the gel undergoes a chemisorption process and reaches equilibrium at 10 h. Moreover, the gel adsorbed arsenic effectively at neutral pH levels and selectively in complex ion environments, achieving a maximum adsorption volume of 1.63 mM/g. The gel could be regenerated with 87.6% efficiency and NaCl could be used for desorption instead of harmful NaOH. Taken together, the presented gel-based design method is an effective approach for constructing high-performance arsenic adsorbents.

In this work, we prepared an adsorbent composed of the cationic N,N-dimethylamino propylacrylamide methyl chloride quaternary (DMAPAAQ) polymer gel and iron hydroxide for adsorbing arsenic from groundwater. The gel was prepared via a novel method designed to ensure the maximum content of iron particles in its structure.

In this work, we prepared an adsorbent composed of a cationic polymer gel containing iron hydroxide in its structure designed to adsorb arsenic from ...