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Controllability of the kinetic path of methane conversion in plasma driven oxidation reaction is investigated. Different geometries in a rotating gliding arc reactor are adopted to control reaction paths in methane oxidation reaction. Diverging and converging type reactor product different reaction environments in view point of both the reaction time and the degree of thermal activation. In the diverging reactor, the partial oxidation process is dominant with high methane conversion because the diverging section facilitates to elongate the arc length and decrease the flow velocity. Thus, the convective and radiative heat transfer from the arc column to the reactants could be enhanced. The role of plasma in the diverging reactor is mainly igniting and sustaining the partial oxidation, which is rather different from that in the converging reactor where the plasma plays as a heat source for thermal pyrolysis of methane with the help of focusing thermal energy of the arc.

Plasma catalysis has been extensively investigated on both plasma and catalyst sides to explore the possible synergies, with most studies focusing on reactivity enhancement and the search for pathways other than those of simple plasma or catalytic reactions. However, there is currently much room for plasma applications beyond reactivity control in catalyst preparation and regeneration phases. This review introduces the use of plasma for accelerated catalyst regeneration and proposes a corresponding mechanistic explanation, showing that the effectiveness of this regeneration can be ascribed to the chemical and/or thermal effects of plasma such as the formation of reactive reductants/oxidants and cost-effective catalyst heat-up. Moreover, plasma-assisted catalyst regeneration is shown to involve low-temperature activation and gas-phase radical–based reactions, be a viable method of avoiding catalyst sintering during conventional high-temperature regeneration, and exhibit the advantage of cost effectiveness.

This study compared the performance of Long Short-Term Memory networks (LSTM) and Soil Water Assessment Tool (SWAT) in simulating observed runoff and projecting future runoff using 11 CMIP6 GCMs. The projected runoff was estimated for two Shared Socioeconomic Pathways (SSPs), 2-4.5 and 5-8.5 for near (2021-2060) and far (2061-2100) futures, respectively. The biases in GCM simulated climate variables were corrected using quantile mapping considering observations at 6 weather stations as reference data over the historical period (1985-2014). Five evaluation metrics were used to quantify the GCM's and hydrological models' capability to reconstruct climate variables and runoff in the Yeongsan Basin of South Korea. Uncertainties in LSTM and SWAT simulated runoff for the historical and projected periods were quantified using Bayesian Model Averaging (BMA) and reliability ensemble averaging (REA), respectively. The results showed significant improvement in bias-corrected GCMs in replicating observations in terms of all evaluation metrics. The extreme runoff estimated using general extreme value (GEV) distribution revealed the better capability of LSTM than SWAT in reproducing observed runoff at all gauging locations. The SWAT projected an increase (17.7%) while LSTM projected a decrease (-13.6%) in the future runoff for both SSPs at most locations. The uncertainty in LSTM simulated runoff was lower than in SWAT runoff at all stations for the historical period. However, the uncertainty in SWAT projected runoff was lower than LSTM projected runoff for both SSPs. This study helps assessing the ability of deep-learning versus physically-based models in hydrological modeling and therefore opens new perspectives for hydrological modeling applications.

Arc plasma has been applied in diverse reactions because it can provide the mechanism for highly thermal activations. However, the efficiency of conversion from electrical energy to thermal energy for the reactant is not sufficiently high, resulting in challenges in practical applications of the arc in various chemical processes. In this study, a method is introduced to enhance the energy usage efficiency for the reactant. The enhancement is based on the control of the arc length elongation. An increase in the arc length results in an enhanced heat transfer from the arc column to the reactant, followed by the reduction of the conductive heat loss to the reactor body. The existing DC arc technologies cannot easily extend the arc length because of the arc instability. However, in this study, a novel AC arc technology was adopted that can support a stable arc with a sufficiently elongated length. Correspondingly, a comparative study on different arc lengths was conducted for the dry reforming (as a model reaction). The increased arc length results in an enhanced heat transfer to the gas or a higher gas temperature. This is followed by the enhancement of the conversions of the reactants for the same supplied electric power. The results provide a firm physical basis for further optimizations of the arc process for chemical reactions.

Hydroxypropyl methylcellulose (HPMC), an FDA-approved water-soluble cellulose derivative, has been used in various wet-adhesion applications in construction products, paints, and drug delivery for 70 years. Despite the various applications, its adhesion mechanism in water has not been elucidated. Here, we measure the adhesion characteristics of HPMC against itself, hydrophilic and hydrophobic surfaces as a function of temperature using a surface forces apparatus (SFA) in water. The results show that HPMC adheres strongly to all tested surfaces, regardless of hydrophobicity. The adhesive strength of HPMC increases with temperature because of entropy-driven hydrophobic interactions and is comparable to or exceeds the wet-adhesion strength of most biological adhesives, including those of mussels and cephalopods. In addition, the elevated temperature induces swelling in HPMC layer, resulting in the exposure of more hydrogen bonding sites, thereby increasing adhesion with the hydrophilic surface. The bulk compression test of the HPMC–silica composite material is consistent with the SFA data and indicates that the water content and temperature are critical variables for the adhesion of HPMC to inorganic surfaces regardless of hydrophobicity. Because adhesive and coating technologies have shifted toward environmentally-friendly systems, these results provide a basis for the fabrication of organic solvent-free HPMC-based composites for future applications.

A novel concurrent process for CO2 reduction and plastic upcycling was successfully developed based on a rotating gliding arc plasma process, where CO2 gas and Low-density polyethylene (LDPE) powder were used as reactants for the process. Herein, the LDPE powder was regarded as an alternative of plastic waste, and the high temperature of the plasma jet thermochemically decomposed the plastic powder. Based on gas chromatography analyses, the yields of the C1 and C2 chemicals were confirmed, which demonstrated the possibility for the chemical upcycling of the plastic powder with CO2 plasma jet. At the same time, the conversion of CO2 at the exhaust gas increased with increasing electric power of the plasma jet. In addition, as the electric power further enhanced, the reverse reactions were efficiently suppressed by the chemical quenching process due to complete depletion of the oxygen by the light hydrocarbon gases generated from the pyrolysis of the plastic powder. Based on the molecular balance of C and O, the calculated syngas to CO2 ratio was achieved up to 32 % in a batch-type plasma reactor with a power supply of 1170 W. It is rational inference that the efficiency will be significantly improved if a plug-in type plasma reactor with higher power supply is implemented. In conclusion, this novel concurrent process would be a promising approach for an efficient and scalable technology of CO2 utilization.

Plasma reforming of fuel has recently been studied for possible applications in hydrogen generation and plasma assisted combustion. However, the kinetic aspects of plasma reforming have not been well understood yet, especially for the reforming of liquid fuels. In this study, a kinetic model was derived for the analysis of diesel partial oxidation assisted by plasma. Using a rotating arc as the plasma source, the effects of the oxygen-to-fuel ratio, specific energy input, temperature, and residence time on the reaction kinetics were investigated. A derived reaction model successfully describes the changes in the selectivity towards hydrogen relative to the amount of energy provided for the generation of plasma and the oxygen-to-fuel ratio in the reforming process.

This study compared the historical and future simulations of precipitation in South Korea from INM-CM4 of Coupled Model Intercomparison Project (CMIP) 5 and INM-CM5 of CMIP6 to identify their differences for the projections of corresponding scenarios by three timeframes (annual, summer and winter) and four regions (NW, NE, SW and SE). Six performance indicators were used to quantify the models' reproducibility to precipitation at 22 stations in South Korea for the historical period (1970–2005). Then, the change rates of precipitations in near and far futures (2020–2059 and 2060–2099) were calculated for two representative concentration pathway (RCP) 4.5 and 8.5 and socioeconomic shared pathway (SSP) 2–4.5 and 5–8.5. Their uncertainties were also quantified using standard deviations and interquartile ranges. As a result, CM5 clearly showed a 7.4% improvement in six performance indicators. The change rates in far future were larger but the uncertainties were smaller. But both the rates and uncertainties in NW were the largest. Also, the uncertainties in INM-CM5 were also smaller than in INM-CM4 for all timeframes and the differences between RCP4.5 and SSP2-4.5 were absolutely larger than those between RCP8.5 and SSP5-8.5.

Recent adhesive technologies have focused on the development of high-quality and eco-friendly adhesives. Thus, there is a gradual shift from the currently used chemical-based adhesives toward harmless adhesives with improved quality and performance. Here, we evaluated the potential use of bacteria-produced recombinant mussel adhesive protein (MAP) as a harmless wood furniture adhesive. We formulated a MAP wood adhesive as an inclusion body type for economical preparation, and we confirmed its harmlessness through the non-detection of volatile organic compounds and heavy metals. The formulated MAP showed sufficiently strong bulk adhesive strength for the dried gluing of wood adherends. We also found that the formulated MAP wood adhesive exhibits robust adhesion in various environmental conditions, including open assembly times, incubation times, temperatures, and humidity levels. In summary, the developed recombinant MAP could be successfully used as a promising environmentally-friendly, harmless wood furniture adhesive.

A plasma process for methane conversion into acetylene is proposed. Acetylene is one of the basic materials used in the chemical industry and its production is predominantly based on chemical processing of naphtha and CaC 2 . The recent increase in shale gas production makes acetylene production from methane a feasible expectation. This study provides data on the lowest cost of acetylene production from methane by a plasma process. The proposed plasma process is based on an effective rotating arc reactor. The rotating arc provides a relatively low reaction temperature, achieving a high carbon balance. Through a study of reaction parameters and the effect of H 2 as a reactant additive, the mechanism of methane conversion was analyzed. The proposed process showed a high efficiency with a minimum process cost of approximately 9 kWh/kg-C 2 H 2 .

Activated carbon has been extensively utilized to adsorb pollutants generated by industrial activities. There have been many attempts to efficiently produce activated carbon from spent coffee grounds in the field of environmental technology. In this study, the feasibility of the novel production of activated carbon from coffee ground waste using a plasma jet was evaluated. A rotating gliding arc generator was designed that used an N2 plasma jet for the carbonization process and a CO2 plasma jet for the activation process. It was confirmed that the coffee ground waste could be carbonized and activated by the two plasma jets in the same reactor. The characteristics of the surface morphologies of the activated carbon samples varied depending on the plasma treatment conditions, such as the electric power of the plasma jet and the treatment time. The results implied that the adsorption capacity of the activated carbon could be optimized by regulating the pore size and distribution based on the plasma treatment conditions with regard to the molecular size of the target adsorbate.

This work investigates the use of plasma-enhanced chemical vapor deposition under atmospheric pressure for achieving uniform layer formation. Electrical and optical measurements demonstrated that the counterbalance between oxygen and precursors maintained the homogeneous discharge mode, while creating intermediate species for layer deposition. Several steps of the deposition process of the layers, which were processed on a stationary stage, were affected by flow stream and precursor depletion. This study showed that by changing the flow streamlines using substrate stage motion uniform layer deposition under atmospheric pressure can be achieved.

As interest grows in methane as a fuel source, its cost-effective activation has become a topic of intensive investigation. As part of these efforts, methane activation using non-thermal plasma was investigated in the presence of various noble gas additives, and the product gases were analyzed. The main products in all cases were alkane species such as C2H6 and C3H8, which were produced independently of the noble gas; however, the conversion of methane was considerably affected by the identity of the noble gas. Because the formation of carbon was a severe problem even in the presence of the noble gases, oxidative methane conversion was also evaluated in terms of the carbon balance and product distribution. By adding oxygen to the methane conversion process, the formation of carbon could be suppressed but the production of higher hydrocarbons was also reduced dramatically. Based on these results, it was concluded that the conversion of methane can be enhanced by varying the discharge characteristics, but the problem of carbon balance must be solved without the addition of oxygen.

This paper reports on controlling the hydrophilicity of polyimide films using atmospheric-pressure homogeneous plasmas by changing only the gas flow rate. The gas flow changed the discharge atmosphere by mixing the feed gas with ambient air because of the particular geometry of the reactor developed for the study, and a low gas flow rate was found to be favorable because it generated abundant nitrogen or oxygen species that served as sources of hydrophilic functional groups over the polymer surface. After low-gas-flow plasma treatment, the polymer surface exhibited hydrophilic characteristics with increased surface roughness and enhanced chemical properties owing to the surface addition of functional groups. Without adding any reactive gases or requiring high plasma power and longer treatment time, the developed reactor with low-gas-flow operation offered effective and economical wettability control of polyimide films.

Plasma-reforming process has been widely studied for over a decade, with a focus on diverse fuels and plasma parameters for finding the optimum conditions. This study evaluates the effect of thermal activation on the chemistry and energy efficiency of the methane-reforming process. Based on the empirical evaluation, a correlation was found among the methane conversion rate, reaction composition, reactant temperature, and plasma power. Moreover, the plasma chemistry did not change with the reactant temperature within the temperature range evaluated. In addition, it was found that the ratio of the plasma power to the heating input power was an important parameter for enhancing the efficiency of the partial oxidation of methane.

Onboard plasma reforming has strong potential for use in supplying reductants for hydrocarbon selective catalytic reduction (HC SCR) of NO x in vehicle exhaust. However, the role of hydrogen as an additional reductant with various catalysts at various temperatures remains unclear. Here we investigated the de-NO x performance of HC SCR with Pt-based and Ag/Al 2 O 3 catalysts at various temperatures using hydrogen and hydrocarbons supplied directly or generated onboard by plasma reforming using engine bench-level tests. Further, we clarified the specific role of hydrogen in the process. We found that with Pt-based catalysts, hydrogen is oxidized to H 2 O or promotes full oxidation of hydrocarbon, thus having no positive effect. By contrast, with Ag/Al 2 O 3 , hydrogen only promotes partial oxidation of hydrocarbon to yield surface intermediates that significantly facilitate SCR. Furthermore, reductants generated by plasma reforming exhibit better de-NO x performance than directly supplied gas mixtures. Thus, onboard plasma onboard reforming can be an important strategy for effective HC SCR.

A plasma-assisted hydrocarbon selective catalytic reduction (HC-SCR) system was constructed and its de-NOx performance was evaluated. An onboard plasma reformer supplied the reducing agent in the system. The reformate gas composition can be varied or the H2/HC ratio can be controlled by controlling the operating conditions. This ratio is important in the SCR process since the performance of the SCR catalyst is dependent on the composition of the reducing agents. Two catalysts were prepared for the test: those having lower-temperature and higher-temperature windows of operation. The proposed system showed a much enhanced de-NOx performance. Onboard plasma reforming enabled achievement of an enhanced de-NOx performance using about half the typical catalyst volume. Fuel penalty of the system remained at ∼3%, with a possibility of further reduction without severe performance degradation. The system volume and power consumption also satisfy conditions necessary for its commercial application. Therefore, it appears suitable for commercial application.

Plasma is receiving attention as a prospective tool for the reforming process of obtaining synthesis gas and hydrogen. Although many reports on plasma-induced reforming have been introduced, detailed correlations between the reaction paths and plasma parameters remain unclear. Therefore, to figure out the relative role and dominance of plasma-controlled chemistry in the reforming process, we investigate diverse reaction paths in reforming CH4. The arc column length is proposed as a universal process parameter of the plasma-reforming process, and a rationale to support the proposition is provided As a result, the dependence of the reforming process on the arc column length is explained. Three different reaction regimes, defined according to the arc column length and plasma chemistry in each regime, are addressed. The arc column length controls the thermal environment of the reaction and activates different reaction pathways depending on its length. This concept of control also enables the discovery of efficient ways of reforming. The increase in thermal efficiency by controlling the arc column reveals possibilities for optimizing the plasma-induced reforming process.

This study investigated the plasma reforming process for diesel focusing on the relative ratio of oxygen to fuel. Excess O 2 in the partial oxidation process is known to increase the combustion portion, resulting in a decreased yield of H 2 and CO. However, in this parametric investigation, there was no apparent decrease in the H 2 and CO selectivity. Adding O 2 did not increase the portion of combustion in the overall reaction. Rather, an excess O 2 supply from partial oxidation stoichiometry resulted in an increase in CO 2 selectivity without a reduction in CO selectivity. Heavy hydrocarbon species were identified as a source of CO 2 in excess O 2 conditions due to preferential oxidative cracking. The additional oxidation of C 1 –C 4 species by excess O 2 provided a minor contribution to CO 2 . Excess O 2 affects soot generation characteristics by suppressing the agglomeration of soot particles, resulting in smaller particle generation. However, the oxidation of soot particles does not provide a major contribution to increasing the CO 2 selectivity. The results show that in a real reforming process, controlling the O 2 supply does not have a strong effect on the process selectivity of hydrogen.

Modern diesel engines have improved engine fuel economy and significantly reduced nitrogen oxides (NOx) and particulate matter (PM) emissions achieved by advances in both combustion and exhaust aftertreatment technologies. Recently, it has been shown that the vehicle emissions can be further improved by several catalytic systems including fuel reformers and aftertreatment systems, such as the Lean NOx Trap (LNT). This NOx removal system, called LNT, absorbs NOx under lean exhaust gas conditions and releases NOx under rich conditions. This technology can provide high NOx conversion efficiency, but the right amount of reducing agent should be supplied into the catalytic converter under appropriate conditions. In this work, plasma reformer was used to supply a hydrogen-enriched gas as a NOx reductant. The plasma reforming is one of the most promising on-board reforming technologies, which allows reformates containing H2 and CO to feed for LNT catalyst efficiently. Partial oxidation is induced by plasma in the fuel reformer and diesel fuel is converted into a hydrogen-enriched gas. The supplying strategy was focused on the maximization of NOx reduction efficiency varying both the total amount of hydrogen-enriched reformate and the ratio of oxygen molecules to in the reformer air-fuel mixture prior to processing at a fixed engine operating condition. The effect of exhaust gas temperature was also studied. The NOx reduction efficiency is closely connected to the amount of supplied fuel to the plasma reformer and the ratio of fuel/air feed rate. The LNT can reduce NOx efficiently with only a 2.6% fuel penalty.

This study investigated two factors affecting the performance of diesel autothermal reforming (ATR): the reforming activity of selected catalysts and the effect of devised fuel delivery apparatuses. When fluorite and perovskite-structured ceramic materials were used as substrates, H 2 yields were higher than when an inert Al 2 O 3 substrate was used at 700–800 °C. Gadolinium (Gd)-doped CeO 2 (CGO) had the highest H 2 production rate in the selected substrates. Platinum (Pt) showed better performance than rhodium (Rh) and ruthenium (Ru) when CGO was used as the substrate. Although the nickel (Ni)-added Pt catalyst (Pt–Ni) showed high H 2 yield, carbon deposition over this catalyst was more severe than with Pt. Oxygen ion (O 2− ) vacancies generated by Gd dopants can enhance the reforming activity of CeO 2 . When using a microchannel catalyst bed, the performance degradation at high gas flowrates can be compared to a packed catalyst bed of pellet type. For effective fuel delivery, we have introduced an ultrasonic injector (UI) and a plasma injector (PI). The UI-reforming showed greater long-term stability than non-UI reforming because the generation of carbon precursors was suppressed. On the other hand, the PI-reformer had low conversion efficiency, although it had high H 2 selectivity.

Simultaneous use of nonthermal plasma and adsorption process for removing volatile organic compounds (VOCs) has been investigated. Toluene (C7H8) and propane (C3H8), which have different adsorption behavior, were treated using three different types of the barrier discharge reactors packed with glass, macro-porous γ-Al2O3, or molecular sieve 5A pellets mixed with the γ-Al2O3 beads, respectively. Test results show that the removal rates of the VOCs treated by nonthermal plasma process increase with the assistance of adsorption. The enhanced removal rates with the adsorption process are maintained under increased temperature conditions, although the adsorption capability is apparently decreased as the temperature increases. In addition, O3 and HNO3 generated from the nonthermal plasma process are significantly decreased with γ-Al2O3 beads, which is another technical advantage to use γ-Al2O3 beads.

Mussel adhesive protein (MAP) fp-151 designed and constructed by our research laboratory has the potential to be used as a cell or tissue bioadhesive at various cell lines in biocompatible aspect. To improve the cell-adhesion and proliferation properties of fp151, we designed an extracellular matrix (ECM) mimics based on mussel adhesive protein fused with biofunctional peptides such as RGD, laminin, type Ⅳ collagen, growth factor called substance P, which is fused at Cterminus of fp151. The ability of adhesion and proliferation properties is tested in several cell lines by direct cell count (DCC) method and MTT assay. Our ECM mimics showed better or similar adhesion and proliferation properties compared with other commercially produced cell-adhesion materials such as poly-L-lysine (PLL) and the naturally extracted MAP mixture Cell-Tak in MC3T3-E1, ATDC5 and 3T3-L1 cells. These data showed that these mimics can be successfully used in cell culture and tissue engineering and extended to other tissuespecific cell recognition motifs to allow attachment of target cells to artificial ECM surfaces.