Gas Contact Research Articles

Characterization of a complex sand-rich gas hydrate reservoir system in the Indian marine continental margin with downhole log and seismic data

Logging-while-drilling (LWD) and coring data were acquired in Areas A, B, C and E during the National Gas Hydrate Program Expedition 02 (NGHP-02). At Sites NGHP-02-16, −17, −20, −23 and −24 of Area B in the Indian Krishna-Godavari Basin, the gas hydrate-bearing sand-rich reservoirs directly in contact with an underlying water-saturated sediment were revealed near the seismic-inferred bottom simulating reflector (BSR) along a large anticlinal structure. Lithofacies analysis of cores show that the lower gas hydrate-bearing reservoir section at these sites is an interbedded unit with thin fine-sand layers alternating with clay-rich layers. We reanalyzed the LWD data including resistivity, compressional-wave and shear-wave acoustic velocities to assess and compare the spatial variation of sand-hosted gas hydrate and possible related free-gas accumulations. The presence of free gas-bearing sediments in direct contact with gas hydrate-bearing sediments was confirmed at Sites NGHP-02-20 and −24 along the northeastern flank of the anticline. The sand-rich reservoirs associated with the Area B anticlinal feature reveal different pore-filling constituents and variable boundary conditions, including gas hydrate/water contacts and gas hydrate/free gas contacts. We infer that the sedimentary depositional history at Sites NGHP-02-20 and −24, may have resulted in an upward shift of the base of gas hydrate stability zone, that could have led to in situ gas hydrate dissociation and the accumulation of free gas and coexistence interval below the log-inferred gas hydrate-bearing reservoir sections. This study demonstrates that reservoir heterogeneity and fluid migration were major factors affecting the distribution of gas hydrate and free gas in the identified sand-rich reservoirs.

CO2 capture from H2O and O2 containing flue gas integrating with dry reforming methane using Ni-doping CaO dual functional materials

Reducing carbon emissions remains a formidable challenge under present energy demands and structures. Integrated CO2 capture and utilisation (ICCU) provides a promising pathway for directly capturing and simultaneously utilising CO2 from the diluted exhaust gas. Dry reforming of methane (DRM) can be integrated into the step of catalytic conversion of the captured CO2 with the advantages of utilising two greenhouse gases to yield valuable syngas (CO + H2). The process has great challenges of materials development for efficient performance, in particular under realistic conditions such as the presence of O2 and H2O in the flue gas. This work investigated the ICCU-DRM using simulated flue gases (10 % CO2 + 6.7 % O2 + 6.0 % H2O) in the presence of Ni-CaO dual functional materials, aiming to optimise Ni loading and metal support interaction. It is found that Ni would significantly sinter and further affect the morphologies of CaO adsorbents, resulting in poorer CO2 capture performances. More notably, the Ni was firstly oxidised during CO2 capture and subsequently went through a pre-reduction period in the DRM step. Increased Ni loading decreased the difficulty of activation; however, it derived in more severe carbon deposition. To avert the direct contact of carbon deposition and flue gas, extra carbon steam gasification was introduced, and higher Ni loading contributed to selectively yielding syngas as a by-product. The Ni10-CaO DFM optimally performed <150 s pre-reduction delay, ∼85 % CO2 conversion and ∼2 H2:CO ratio in the DRM step and ∼75 % CO selectivity in the CSG step at 650 °C. The interaction between Ni and CaO poorly contributes to the performance due to the poor reducibility and accessibility, and the Ni particle size effects only play as spectators in this integrated process.

Dry Water as a Promoter for Gas Hydrate Formation: A Review.

Applications of clathrate hydrate require fast formation kinetics of it, which is the long-standing technological bottleneck due to mass transfer and heat transfer limitations. Although several methods, such as surfactants and mechanical stirring, have been employed to accelerate gas hydrate formation, the problems they bring are not negligible. Recently, a new water-in-air dispersion stabilized by hydrophobic nanosilica, dry water, has been used as an effective promoter for hydrate formation. In this review, we summarize the preparation procedure of dry water and factors affecting the physical properties of dry water dispersion. The effect of dry water dispersion on gas hydrate formation is discussed from the thermodynamic and kinetic points of view. Dry water dispersion shifts the gas hydrate phase boundary to milder conditions. Dry water increases the gas hydrate formation rate and improves gas storage capacity by enhancing water-guest gas contact. The performance comparison and synergy of dry water with other common hydrate promoters are also summarized. The self-preservation effect of dry water hydrate was investigated. Despite the prominent effect of dry water in promoting gas hydrate formation, its reusability problem still remains to be solved. We present and compare several methods to improve its reusability. Finally, we propose knowledge gaps in dry water hydrate research and future research directions.

Endothermic relaxation behavior of gangue in longwall gob: Bidirectional heat transfer model and its simulation validation

The collapse of overlying strata in a goaf during coal mining forms many gangue blocks that vary in size and shape. Because the heat released by the coal–oxygen reaction diffuses around the wind flow, endothermic relaxation occurs when the heated gas contacts the gangue. However, only a few studies have addressed this issue. In this study, we first propose a method to investigate the thermal relaxation behavior by expanding the mathematical space of the problem and then establish a bidirectional heat transfer model of a single-gangue-ball in spherical coordinates combined with the energy conservation law, which is solved numerically using the finite difference method. Finally, the reason for the fluctuation of the solid temperature distribution in the gob is determined by extracting the calculation results and comparing them with the gangue temperature curve under transient heat conduction, and the effects of some key factors on the thermal relaxation efficiency of the gangue are quantitatively investigated. The results show that (i) along the high-temperature path of the goaf, the gangue temperature exhibits the same trend as the ambient temperature, and its external and internal temperature difference decreases gradually with an increase in burial depth; (ii) compared with the change in temperature rise under transient heat conduction, the relaxation phenomenon can result in a calculation error of up to 1.3 °C; (iii) the heat transfer efficiency is related to the gangue characteristics and its surface heat transfer resistance, and the accuracy of spontaneous combustion prediction can be guaranteed by increasing the initial temperature, reducing the heat transfer radius, or decreasing the air flow rate. In this study, the thermal relaxation behavior of the gangue in a gas–solid dual medium in a longwall gob is investigated, and a foundation is laid for the establishment of a four-dimensional temperature field model for the gangue in the future.

Analyses and studies for the selection of the method of dual completion operation of wells in multi-layer fields

Mandatory research and measurement complexes for monitoring development should cover evenly the entire area of the development object, the entire fund of observation wells. They should contain measurements of reservoir pressure for control and piezometric wells, measurements of reservoir and bottom-hole pressures, well flow rates for liquid, gas factors and water content of products for producing wells, measurements of wellhead injection pressures and injection volumes for injection wells, hydrodynamic studies of producing and injection wells in stationary and non-stationary modes, studies on the control of the oil and water contact, gas and oil contact, oil and gas saturation, technical condition of the wellbore by field-geophysical methods, selection and research of deep oil samples, surface rock products of wells (oil, gas, water).&#x0D; The paper considers in detail proposals to improve the system of collection, preparation and transport of natural, associated gas and condensate. The topic of operation of gas wells, the state and proposals for improving the system of gas and condensate collection and treatment, requirements for structures, drilling technology, the method of reservoir opening and well development on the example of the Altyguyi gas condensate field is touched upon. The choice and justification of the well design in accordance with the intervals of compatibility of the well section according to mining and geological drilling conditions based on the forecast curves of reservoir pressures and rock rupture pressures (combined pressure graph), as well as methods of primary and secondary opening of productive formations and their development are considered in detail.

Fully Flexible MXene-based Gas Sensor on Paper for Highly Sensitive Room-Temperature Nitrogen Dioxide Detection.

Flexible chemiresistive gas sensors have attracted growing interest due to their capability in real-time and rapid detection of gas. However, the performance of gas sensors has long been hindered by the poor charge transfer ability between the conventional metal electrode and gas sensing semiconductors. Herein, for the first time, a fully flexible paper-based gas sensor integrated with the Ti3C2Tx-MXene nonmetallic electrode and the Ti3C2Tx/WS2 gas sensing film was designed to form Ohmic contact and Schottky heterojunction in a single gas sensing channel. Ti3C2Tx/WS2 has outstanding physical and chemical properties for both Ti3C2Tx and WS2 nanoflakes, showing high conductivity, effective charge transfer, and abundant active sites for gas sensing. The response of the gas sensor to NO2 (1 ppm) at room temperature is 15.2%, which is about 3.2 and 76.0 times as high as that of the Au interdigital electrode integrated with the Ti3C2Tx/WS2 sensor (4.8%) and the MXene electrode integrated with the Ti3C2Tx sensor (0.2%), respectively. Besides, this design performed at a limit of detection with 11.0 ppb NO2 gas and displayed excellent stability under high humidities. Based on first-principles density functional theory calculation results, the improvement of the gas sensing performance can be mainly attributed to the heterojunction regulation effect, work function matching, and suppressing metal-induced gap states. This work provides a new approach for the design of flexible gas sensors on paper with MXene-based conductive electrodes and gas sensing materials.

Unveiling the High-valence Oxygen Degradation Across the Delithiated Cathode Surface.

Charge compensation on anionic redox reaction (ARR) has been promising to realize extra capacity beyond transition metal redox in battery cathodes. The practical development of ARR capacity has been hindered by high-valence oxygen instability, particularly at cathode surfaces. However, the direct probe of surface oxygen behavior has been challenging. Here, the electronic states of surface oxygen are investigated by combining mapping of resonant Auger electronic spectroscopy (mRAS) and ambient pressure X-ray photoelectron spectroscopy (APXPS) on a model LiCoO2 cathode. The mRAS verified that no high-valence oxygen can sustain at cathode surfaces, while APXPS proves that cathode electrolyte interphase (CEI) layer evolves and oxidizes upon oxygen gas contact. This work provides valuable insights into the high-valence oxygen degradation mode across the interface. Oxygen stabilization from surface architecture is proven a prerequisite to the practical development of ARR active cathodes.

Unveiling the High‐valence Oxygen Degradation Across the Delithiated Cathode Surface

AbstractCharge compensation on anionic redox reaction (ARR) has been promising to realize extra capacity beyond transition metal redox in battery cathodes. The practical development of ARR capacity has been hindered by high‐valence oxygen instability, particularly at cathode surfaces. However, the direct probe of surface oxygen behavior has been challenging. Here, the electronic states of surface oxygen are investigated by combining mapping of resonant Auger electronic spectroscopy (mRAS) and ambient pressure X‐ray photoelectron spectroscopy (APXPS) on a model LiCoO2 cathode. The mRAS verified that no high‐valence oxygen can sustain at cathode surfaces, while APXPS proves that cathode electrolyte interphase (CEI) layer evolves and oxidizes upon oxygen gas contact. This work provides valuable insights into the high‐valence oxygen degradation mode across the interface. Oxygen stabilization from surface architecture is proven a prerequisite to the practical development of ARR active cathodes.

Rational design of hierarchically micrometer scaled macro-mesoporous ceria-zirconia composites for enhancing diesel soot catalytic combustion performance

Diesel soot particulate is the primary source of urban atmospheric fine particulate matters (PM2.5), catalytic soot elimination on diesel participate filter is invariably an important yet challenging subject, because of the inherently poor solid-solid contact of soot-catalyst. In this study, we report a hierarchically porous ceria-zirconia composite with micrometer scaled macroporous structure, CZ-8, for enhancing catalyst-soot contact efficiency and soot catalytic combustion performance. Scanning electron microscope (SEM), N2 adsorption-desorption and mercury porosimetry results demonstrate that the CZ-8 catalyst has definite micrometer scaled macroporous (0.5–5.0 μm) and interconnected mesoporous (∼20 nm) structure. Raman and X-ray diffraction (XRD) results show that the dominant crystal structure of the CZ-8 is cubic fluorite and the relatively larger crystalline grain contribute to the macroporous structure construction. The filamentous diesel soot particulate (hundreds nanometers or even several micrometers) is difficult to enter the pores of the conventional mesoporous ceria-zirconia catalysts. Nonetheless, it can enter the micrometer scaled pores of the CZ-8 and hence improve the soot-catalyst contact efficiency, and oxygen can efficiently contact with soot-catalyst through the mesopores. Accordingly, the CZ-8 catalyst displays a significantly lower light-off temperature and better soot catalytic combustion performance under loose and tight contact conditions. Thus, this work suggests that enhancing solid(soot)-solid(catalyst)-gas(oxygen) contact efficiency by hierarchically porous structure with micrometer scaled macropores of catalyst is a promising new pathway for improving soot catalytic combustion performance and controlling diesel exhaust particulate emissions.

Study the influence of the carbon dioxide content in the composition of the working agent of hydrocarbon gases on the condensates evaporation

This article analyzes the volatility of retrograde condensate when a gas condensate field is exposed to dry natural gases containing carbon dioxide (CO₂), which is associated with some of its advantages over other non-hydrocarbon gases.&#x0D; The indicators of the process of impact on the bottomhole zone of a producing gas condensate well by "dry" gas enriched with carbon dioxide are studied, taking into account the influence of the physicochemical and thermodynamic properties of the gas condensate system, as well as the thermobaric conditions of the process itself.&#x0D; "Dry" hydrocarbon gas containing carbon dioxide more actively evaporates retrograde condensate compared to other non-hydrocarbon gases. However, to increase the efficiency of this process, one should take into account the number of injected gas contacts and the temperature of the bottomhole zone.

Maximum aerobic speed, maximum oxygen consumption, and running spatiotemporal parameters during an incremental test among middle- and long-distance runners and endurance non-running athletes.

BackgroundMaximal aerobic speed (MAS) is a useful parameter to assess aerobic capacity and estimate training intensity in middle- and long-distance runners. However, whether middle- and long-distance runners reach different levels of MAS compared to other endurance athletes with similar V̇O2max has not been previously studied. Therefore, we aimed to compare V̇O2max, MAS and spatiotemporal parameters between sub-elite middle- and long-distance runners (n = 6) and endurance non-runners (n = 6). In addition, we aimed to compare the maximal blood lactate concentration [BLa] experienced by participants after conducting these tests.MethodsTelemetric portable respiratory gas analysis, contact and flight time, and stride length and rate were measured using a 5-m contact platform during an incremental test at a synthetic athletics track. V̇O2, heart rate, respiratory quotient values in any 15 s average period during the test were measured. [BLa] was analyzed after the test . Running spatiotemporal parameters were recorded at the last two steps of each 400 m lap. A coefficient of variation (%CV) was calculated for each spatiotemporal variable in each participant from 8 km h−1 onwards.ResultsWhereas runners reported faster MAS (21.0 vs. 18.2 km h−1) than non-runners (p = 0.0001, ES = 3.0), no differences were found for V̇O2max and maximum blood lactate concentration during the running tests (p > 0.05). While significant increases in flight time and stride length and frequency (p < 0.001, 0.52 ≤ n}{}{eta }_{p}^{2} ≤ 0.8) were observed throughout the tests, decreases in contact time (p < 0.001, n}{}{eta }_{p}^{2}=0.9) were reported. Runners displayed a greater %CV (p = 0.015) in stride length than non-runners. We conclude that middle- and long-distance runners can achieve a faster MAS compared to non-running endurance athletes despite exhibiting a similar V̇O2max. This superior performance may be associated to a greater mechanical efficiency. Overall, runners displayed a greater ability to modify stride length to achieve fast speeds, which may be related to a more mechanically efficient pattern of spatiotemporal parameters than non-runners.

Relating Crystal Structure to Surface Properties: A Study on Quercetin Solid Forms.

The surface energy and surface chemistry of a crystal are of great importance when designing particles for a specific application, as these will impact both downstream manufacturing processes as well as final product quality. In this work, the surface properties of two different quercetin solvates (quercetin dihydrate and quercetin DMSO solvate) were studied using molecular (synthonic) modeling and experimental techniques, including inverse gas chromatography (IGC) and contact angle measurements, to establish a relationship between crystal structure and surface properties. The attachment energy model was used to predict morphologies and calculate surface properties through the study of their growth synthons. The modeling results confirmed the surface chemistry anisotropy for the two forms. For quercetin dihydrate, the {010} facets were found to grow mainly by nonpolar offset quercetin–quercetin stacking interactions, thus being hydrophobic, while the {100} facets were expected to be hydrophilic, growing by a polar quercetin–water hydrogen bond. For QDMSO, the dominant facet {002} grows by a strong polar quercetin–quercetin hydrogen bonding interaction, while the second most dominant facet {011} grows by nonpolar π–π stacking interactions. Water contact angle measurements and IGC confirmed a greater overall surface hydrophilicity for QDMSO compared to QDH and demonstrated surface energy heterogeneity for both structures. This work shows how synthonic modeling can help in the prediction of the surface nature of crystalline particles and guide the choice of parameters that will determine the optimal crystal form and final morphology for targeted surface properties, for example, the choice of crystallization conditions, choice of solvent, or presence of additives or impurities, which can direct the crystallization of a specific crystal form or crystal shape.

Different Welding Processes Using Statistical and Numerical Approaches Using the Fuzzy TOPSIS Method

Welding is for two or more parts heat; pressure or Linking is a fabrication process cooling of parts. Welding usually involves metals and Used in thermoplastics, but also in wood can be used. A finished welded joint May be referred to as good material. Welding such as metals, thermoplastics, and/or wood Applying heat or pressure to materials It is a process of joining them together. Cool those down Allow enable the connection. Different Processes and techniques unique to materials required there are some people items that are considered unusable. MIG welding uses an electrode wire and shield gas fed continuously through A lamp held in the hand. A consumable for TIG welding is tungsten uses an electrode, which is a supply line, and Shield through a separate, hand-held filler wire manually injected into the weld pool with gas. Research significance: Welding is two or more parts by heat, pressure, or both together Linking is a fabrication process. Welding is usually in metals and thermoplastics used, but can also be used on wood. The finished welded joint may be referred to as a weld meant. Gas pressure welding joins two base materials in under pressure by heating them with gas contact. Resistance spot welding two Combine the basic ingredients together heating up with heat generated by electrical resistance by conducting current. The basic purpose of welding is within a solid joint combining two elements. Welders in general Work with metal or thermoplastic and durable filler material to hold together are using Skyscrapers in our world, many modern ones like cars, ships, and planes Welding is used to make structures. Mythology: Alternative: Factorial designs, ANNs, GA, and RSM. Evaluation Option: Computational time, Experimental domain, Model developing, Availability in software, Optimization Accuracy level. Result: from the result it is seen that Model developing and is got the first rank whereas is the Availability in software got is having the lowest rank. Conclusion: The value of the dataset for Welding Process in Fuzzy TOPSIS method shows that it results in Model developing and top ranking.

Improvement of Hydrogen Sulfide Scavenging via the Addition of Monoethanolamine to Water-Based Drilling Fluids.

The release of the lethal hydrogen sulfide (H2S) gas during the drilling of sour subterranean formations is of huge health and safety concern. Additionally, the contact of this corrosive gas with handling equipment might result in severe damages and significant economic losses. Accordingly, effective in situ scavenging of H2S while drilling is very crucial. Thus, we report herein the addition of monoethanolamine (MEA) to water-based mud with the objective of improving the H2S-scavenging efficacy of the mud. The H2S-scavenging capacity was evaluated for the MEA-containing mud and compared with the base mud and fluids containing the commercial scavengers, SourScav and triazine. Also, the key mud characteristics including rheology, filtration properties, alkalinity, and corrosion rate were investigated in the presence and the absence of MEA, and the obtained results were compared to those of SourScav and triazine. The obtained experimental results revealed that the addition of MEA to the base mud significantly improved the H2S adsorption capacity of the base mud by 117%, compared to 50 and 74% with the SourScav and triazine. Additionally, the pH value of the MEA-containing mud complied with the practical recommendations for drilling in a sour environment. Moreover, the plastic viscosity was increased by 13% to 37 cP with the MEA-containing mud with an insignificant impact on the yield point. Furthermore, the MEA-containing mud showed a favorable zero corrosion rate, as was the case for SourScav and triazine muds. However, unlike SourScav and triazine, MEA did not substantially enhance the filtration performance. Nonetheless, the filtration characteristics of the MEA-containing mud were still better than the base mud and within the recommended practical range for water-based muds. Overall, the results presented in this study reveal that the addition of monoethanolamine to water-based muds improves the mud characteristics and, more importantly, provides a superior H2S-scavenging performance relative to SourScav and triazine scavengers, suggesting the commercial relevance of MEA for drilling applications.

Well Log Lithological Analysis and Petrophysical Parameters Calculation of Miocene to Recent Formation Reservoirs in Well P10, Offshore, Northern Rio Del Rey Basin (Southwest Cameroon, Gulf of Guinea)

The P10 well is located offshore, in the Northern part of the Rio Del Rey basin in southwest Cameroon. Although the Rio Del Rey basin is the most prolific coastal basin in Cameroon given the production results from several fields in the southern part, yet it remains very little explored in its northern part. This work evaluation the petroleum potential in the northern part of the Basin using a combination of the &amp;quot;Quick Look&amp;quot; interpretation of the logs recorded in well P10 and &amp;quot;complex matrix&amp;quot; facies analysis of the different lithofacies through the neutron porosity - bulk density (NPHI-RHOB) and delta time sonic - bulk density (DT-RHOB) diagrams. The composite log includes the Gamma Ray log; Caliper log; Deep Resistivity log; neutron porosity log and bulk density log. In addition to this composite log, a geological end of well report is completed to refine the results. Ten (10) near sand/sandstone reservoirs were delineated between 950 and 1803 TVD m (true vertical depth in meter) with very good porosities (12% &amp;lt;&amp;Phi;&amp;lt; 30%) as well as a mineralogical composition dominated by quartz. Clay volumes are relatively lower than 18% except in reservoirs R5 and R6 where they are around 24%, giving the latter a sandy-clay lithology. Reservoirs R2 and R4 contain oil, the latter with a WOC (Water Oil Contact) at ~1172 m and a GOC (Gas Oil Contact) at 1169 m. Reservoirs R6; R7; R8; R9; R10 all contain Gas and Water with WGC (Water Gas Contact) located at ~1431 m; 1530 m; 1690 m and ~1790 m respectively. In the light of these results, there is a clear dominance of gaseous hydrocarbon reservoirs over oil-impregnated ones in the study area. The results provided by this work can serve as baseline data for future oil and gas exploration projects in the northern part of the Rio Del Ray Basin.

A Review: Contact Electrification on Special Interfaces

The contact electrification of materials plays an important role in developing and applying triboelectric nanogenerators (TENGs). By exploring the contact electrification phenomena at different interfaces, we can improve the understanding of the electrification mechanism and expand the application field of TENGs. In this way, the rate of energy utilization can be improved while the harm caused by the electrostatic effect is reduced. This article systematically summarized the different interface contacts between the research status quo of electricity. This article expounds the solid–solid interface, liquid–solid interface, and liquid–liquid interface, as well as the gas and other interface contact electrification mechanism, and the research and application of these are introduced; finally, it prospects the contact between the different interfaces of electric potential applications as well as the challenge.

Compatibility of Environmentally Friendly Insulating Gases CF3I and c-C4F8 with Cu Contacts

The gas-solid compatibility between environmentally friendly insulating gas and copper contacts is worth studying. In this paper, based on density functional theory, the adsorption calculation of CF3I, c-C4F8, five typical decomposition gases, and Cu (1 1 1) surface was carried out. The adsorption energies, transferred charges, charge densities, and densities of states were calculated for different adsorption configurations. Research indicates that there is no obvious charge transfer between the I atom and the Cu atom in the four adsorption sites of Cu (1 1 1) for the CF3I molecule. There is a charge transfer between the F atoms and the Cu top surface. The electrons lost by Cu are transferred to F atoms. In the configurations of different adsorption positions on CF3I and Cu (1 1 1) planes, the top and bridge adsorption energies are −0.835 eV and −0.993 eV, respectively, which are chemical adsorption. Therefore, CF3I is most likely to form adsorption at the top or bridge site of the Cu (1 1 1) surface. The adsorption energy of c-C4F8 gas on Cu (1 1 1) surface is similar to that of CF3I at fcc and hcp sites. The absolute values are all less than 0.8 eV, and the van der Waals force is the main force. The adsorption energies of C2F4 and C3F6 in the five decomposed gases are −1.315 eV and −1.204 eV, respectively. The charge transfer is −0.32 eV and −0.45 eV, respectively. Their values are larger than those of the other gases studied, which belong to chemical adsorption. The smaller values of the remaining three gases belong to physical adsorption. All molecular structures and Cu (1 1 1) planes were not significantly deformed. From a microscopic point of view, the gas can better exist on the copper surface.

Enhanced CO2 sequestration based on hydrate technology with pressure oscillation in porous medium using NMR

Carbon dioxide (CO2) is a dominant greenhouse gas in the atmosphere that contributes to global warming. A promising approach to mitigate CO2 emissions is CO2 capture and storage (CCS) through clathrate hydrate crystallization under the seafloor; however, numerous issues regarding the mechanisms of concentration, efficiency, and stability of CO2 hydrate sequestration in seafloor sediments remain under dispute. This study employed low-field nuclear magnetic resonance (NMR) measurements to observe the in-situ formation of CO2 hydrate using the pressure oscillation method in porous media and evaluate the carbon sequestration efficiency. Our results indicate that CO2 hydrates are preferentially formed in large pore spaces, further hindering the subsequent gas contact with water in isolated pores. Additionally, a high initial water saturation is more conducive to high-quantity CO2 hydrate capture and sequestration in a pressure variation environment with a higher driving force. The proposed pressure oscillation method could effectively break the mass transfer barriers in the later stage of hydrate formation with the help of CO2 solubility fluctuations, significantly increase the rate of later hydrate formation, and shorten the period of hydrate sequestration.

Asymmetric power dissipation in electronic transport through a quantum point contact

We investigate the power dissipated by an electronic current flowing through a quantum point contact in a two-dimensional electron gas. Based on the Landauer-B\"uttiker approach to quantum transport, we evaluate the power that is dissipated on the two sides of the constriction as a function of the Fermi energy, temperature, and applied voltage. We demonstrate that an asymmetry appears in the dissipation, which is most pronounced when the quantum point contact is tuned to a conductance step where the transmission strongly depends on energy. At low temperatures, the asymmetry is enhanced when the temperature increases. An estimation for the position of the maximum dissipation is provided.

A New Method for Capturing CO2 from Effluent Gases Using a Rice-Based Product

In 2013, UAE imported around 772 million kilograms of rice, making it one of the largest consumers of this popular grain in the world. However, 40% of rice available in the market is discarded, contributing to the country’s CO2 footprint. Given that CO2 emissions are recognized as a significant contributor to climate change and efforts aimed at their reduction are proving insufficient for combatting the global increase in temperature, various approaches aimed at its removal from the atmosphere have been proposed. The goal of this study is to contribute to this initiative by proposing a new method for CO2 removal based on a special gas contact device filled with buffered puffed rice cakes obtained by heating in a purposely designed sealed chamber at high pressure to obtain layers with 9−12 mm thickness. The resulting cakes are subsequently immersed in a sodium hydroxide liquor (0.25−2.5 M) to increase the moisture content to 5% and pH to &gt;11.0. In the experiments, different rice structures (stacked layers, rice grains, and multi-spaced layers) were tested, varying the CO2 percentage in the simulated effluent gas (1−15%). The highest CO2 uptake value (7.52 × 10−3 mole CO2/cm2 rice cake surface area) was achieved using 10% CO2 and a 500 mL/min flow rate with rice cakes of 80 mm diameter, comprising 12 mm thick layers that occupied 20% of the device volume. These results indicate that the proposed design exhibits high CO2 removal efficiency and should be further optimized in future investigations.