Variation Of Gas Concentration Research Articles

Effect of air supplementation on the performance of an onboard catalytic inerting system

In this work, a catalytic inerting process with an external air supplement was proposed. Based on the molar flow rate of the pumped air in the fuel tank, the flow relationship of each gas component after flowing through the catalytic reactor was derived. The mathematical model of the gas concentration variation in the gas phase space of the tank was established by considering the mass conservation equation and gas equilibrium dissolution relationship, and the core fuel tank model was verified using existing experimental data. The performances of the inerting system for aviation fuels, such as JP8, RP3 and RP5, with and without an external air supplement were compared and studied, and the influence of the key parameters on the performance of the system was determined. The results indicated that the presence of an air supplement can accelerate the process of inerting; a higher fuel vapor pressure corresponds to the requirement for a larger air supplement ratio, which means that more inert gas flow is generated by the reaction and the O2 concentration of the tank decreases more rapidly. For example, when the inerting system of RP5 has a catalytic efficiency of 0.8, the O2 concentration in the gas phase of the tank decreases to 9%; the time required for this process without and with the air supplement is 7.55 min and 0.77 min, respectively. Under the same conditions, the highest inerting rate is for RP5, followed RP3 and JP8. In addition, with the air supplement, the inerting time of the RP3 and RP5 fuels is reduced with the increase of the catalytic efficiency. A larger fuel loading rate corresponds to a smaller gas phase space volume and less inerting time. The inerting time is inversely proportional to the fan flow rate, that is, when the flow rate of the fan increases by N times, the inerting time decreases to 1/N times the original value. Therefore, when designing an onboard catalytic inerting system, the inerting performance can be improved by providing an external air supply, and the influence of the key parameters, such as the catalytic performance, fuel loading rate and fan flow, on the system performance should be considered.

Gas barrier mechanism in non-ventilation excavation

Gas overruns and explosions often occur in coal mining. To deal with this problem, the spatial structure model of a new non-ventilation excavation system is constructed. Combined with the model, a simulation experiment is conducted and the variations in gas concentration in each area of the system with variations in the amount of gas emission, drainage, and nitrogen curtain outlet velocity are obtained. The effectiveness of the gas barrier by the combined action of the gas drainage and nitrogen curtain is verified. This study provides the experimental basis for solving the problem of gas overruns and explosions, and is of great significance for realizing safe, efficient, and rapid excavation.

Study on Characteristics of Airflow Spatial Distribution in Abandoned Mine Gob and Its Application in Methane Drainage

At present, there are many known sources of methane resources in abandoned mine gobs. Therefore, investigations into the characteristics of airflow spatial distributions in abandoned mine gobs will be helpful in future methane drainage processes. In this study, a physical simulation experiment was first adopted to simulate the formation processes of abandoned gobs based on the geological conditions of the abandoned Yongan Mine in China. Gas injection experiments were then conducted to study the gas concentration distributions and variations in a simulated gob based on the measured gas concentrations at certain sampling points. The results indicate that the abandoned gob comprises a gas enrichment zone (GEZ), gas diversion zone (GDZ), and gas isolation zone (GIZ) from the bottom to the top in the incline edges of the abandoned gob, respectively. However, only the GEZ and GIZ exist in the incline center of the abandoned gob. The gas concentration in the GEZ is observed to be the highest, although the concentration is also found to be relatively high in the GDZ. Moreover, a shielding is found to exist between the boundaries of the GEZ and GDZ, which results in a dramatic decline in concentration in the latter due to its extremely low permeability. The study results were verified by using the methane drainage data from the surface vertical wells in the abandoned Yongan Mine. The field application indicated that the methane extraction flow rate could potentially increase by 1.5 times when the well bottom traversed the GDZ and entered the GEZ, compared to the flow rate when the well bottom was located in the GDZ.

Prediction of gas and coal spontaneous combustion coexisting disaster through the chaotic characteristic analysis of gas indexes in goaf gas extraction

The gas and coal spontaneous combustion coexisting disasters have become a common mode of major and extraordinarily serious accident of coal mine, so it has important significance to predict the coexistence disaster for prevention and treatment. This study took the gas samples from gas drainage pipeline in the goaf of 1203 working face of Hongyang No. 2 Coal Mine, and then analyzed the chaotic characteristics of coal gas indexes from gas drainage pipeline by using the R/S analysis method. The results show that the Hurst index of time series of gas indicators related to coal spontaneous combustion shows stable statistical characteristics when the oxygen concentration fluctuates smoothly. However, when the oxidation of coal in goaf accelerates, the Hurst index will be smaller than 0.77025. The Hurst index of time series of gas indicators related to gas in the goaf of 1203 working face is greater than 0.5, which indicates that gas has persistent correlation. The Hurst index can quantitatively reflect the inherent tendency characteristics and persistent intensity of the gas concentration variation process. The Hurst index of time series of gas indicators related to coal spontaneous combustion at the monitoring point can be used to judge the time tendency of coal spontaneous combustion in goaf and further judge the spontaneous combustion state of coal. Therefore, methods for judging whether the coal in goaf is in the dangerous stage of spontaneous combustion and for determining the change trend of gas concentration in the goaf were proposed. On this basis, the coexisting disaster were forecasted, moreover, this kind of prediction method can reduce the misinformation of the coexisting disaster. The study provides a meaningful new idea and method for improving the theory of coexisting disaster prediction.

Model development for microbial spoilage of packaged fresh‒cut salad products using temperature and in-package CO2 levels as predictor variables

The objective of this study was to develop a model system for the prediction of the impact of temperature and in-package % CO2 on the microbial spoilage of fresh‒cut vegetables with high respiration rate independent of packaging characteristics and post-harvest physiology. Model development was based on study of rocket pulp stored under 0–20% O2: 20-0% CO2: 80% N2 at 0–15 °C. Growth of pseudomonads and lactic acid bacteria (LAB) was primary modelled by Baranyi model, while growth rate was further modeled as a function of storage temperature and % CO2 by a polynomial model. Both growth models were validated against various fresh‒cut vegetables of high respiration rate, modified atmosphere packaging, and packaging films, under isothermal and dynamic temperature conditions. Variations of gas concentration of rocket pulp was eliminated or significantly decreased (p < 0.05), verifying our initial hypothesis. Pseudomonads were the dominant spoilage microorganisms in rocket pulp, while LAB were significantly favored (p < 0.05), as temperature and % CO2 increased. Both models had acceptable performance, presenting pRE (proportion of relative error) ≥ 0.70, bias factor of 0.99–1.00 and accuracy factor of 1.04–1.07. The developed empirical models in rocket pulp may be a useful tool to predict pseudomonads and LAB behavior in commercial packages of different fresh‒cut salads such as rocket, romaine, and iceberg lettuce.

Fabrication of a WO3 Conductometric Activated Thin Film Sensor for Resistance-to-frequency Conversion Based Sensing Application

In this paper, we propose and experimentally evaluate the feasibility of incremental frequency change due to change in contact gas percentage, as a sensing parameter for WO3 based thin film ethanol detector. In the present work, an economic but accurate ethanol detection system has been realized along with a signal conditioning circuit where a timing resistance of a 555 timer is constituted by a WO3 based thin film sensor. The incremental resistance change due to the variation of gas concentration results in the change in frequency of the astable multivibrator. Finally, by measuring the frequency using an oscillator, the ethanol percentage can be estimated. The whole system is simple and can be realized with only a few hardware components. Further, accuracy has been enhanced using the Pd and Pt modified WO3 based thin film sensor.

Underground coal gasification – A numerical approach to study the formation of syngas and its reactive transport in the surrounding strata

In this work, a method to study the formation of syngas during the underground coal gasification (UCG) process and its reactive transport in the surrounding strata is proposed. It combines a thermodynamic equilibrium stoichiometric model of the cavity reactions with a coupled thermo-hydraulic-chemical–mechanical (THCM) framework of COMPASS code for the transport of UCG products away from the cavity. With the input information of coal properties obtained from the South Wales coalfield, gasification reagents (air and steam) and thermodynamic conditions (initial temperature and pressure), the thermodynamic equilibrium model developed provides the maximum yield of gasification products and temperature from a UCG system. Gasification results giving the syngas composition with the highest percentage of methane and carbon dioxide, are then used as the chemical (gas) and thermal boundary conditions for the coupled thermo-chemical model of the THCM framework to analyse the variations of temperature and gas concentrations, in strata surrounding the UCG reactor. For that purpose, a set of numerical simulations considering three porous media (coal, shale and sandstone) with different physico-chemical properties is conducted. The gasification results demonstrate that increasing the amount of steam injected in the UCG reactor decreases the temperature of the system as well as the concentration of carbon monoxide and nitrogen, while benefiting the production of hydrogen, methane and carbon dioxide. The numerical simulations performed using the THCM model indicate that multicomponent gas diffusion and advection are competing transport mechanisms in porous media with intrinsic permeability higher than 1 mD (sandstone), while the gas diffusion becomes a dominant transport process in porous media with an intrinsic permeability lower than 1 mD (coal and shale). Moreover, the simulation results of reactive transport of methane and carbon dioxide in different porous media demonstrate the significance of considering the adsorption effect in the gas transport in the overall UCG process. In particular, the retardation of the gas front due to gas sorption is the most pronounced in coal, followed by shale and then sandstone. In conclusion, the model presented in this study demonstrates its potential application in managing the environmental practices, reducing pollution risk and securing greater public and regulatory support for UCG technology.

Monitoring Real Time, In-Line Variations of Noble Gas Concentrations During CO2 Capture Operations by Means of a Portable Mass Spectrometer

In the ICO2P-project the overall aim is to develop an innovative and cost-effective monitoring scheme for CO2 capture and storage operations, implementing new methods for in situ noble gas measurements. The first step is to establish a basis for fluid source identification by recording temporal variance of noble gas composition in CO2 product. Studies of noble gases related to CCS typically include few, single point samples. In ICO2P, a portable mass spectrometer (i.e. miniRUEDI) is utilized to directly measure real time variability of the noble gas content in CO2 gas streams at operating CCS facilities. The first study was performed at the Technology Centre Mongstad (TCM) in Norway, a large-scale test facility for post-combustion CO2 capture operations. During an open scientific test campaign for amine-based capture (TSA-MEA), noble gases (He, Ar, Kr) as well as CO2, N2, O2 concentrations in the CO2 product stream were recorded every 10 to 15 minutes during a 5-day period. He concentrations (<0.001ppm)were depleted post-capture and too low for temporal variation measurements in the CO2 product line. Ar concentrations (0.15 – 0.65 ppm) were significantly higher and temporal variation was successfully recorded in the CO2 product line. Ar was found to be sensitive to capture operations, e.g. CO2 recycling ratio. This new approach will provide knowledge of the uniqueness and variability of inherent noble gas fingerprints and depletion/absorption during CCS operations and provide grounds for comparison between fluid origins needed in leakage detection schemes at CO2 storage sites.

Relation Between Fracture Stability and Gas Leakage into Deep Aquifers in the North Perth Basin in Western Australia.

The Kockatea Shale is a proposed target for unconventional gas development in the North Perth Basin in Western Australia. This research is concerned with correlating the extent of thermogenic gas leakage into deep aquifers overlying the Kockatea Shale with an assessment of how close the formation is to mechanical failure. Data from two petroleum exploration wells located approximately 20 km apart were considered. Both have comparable stratigraphy; however, they differ by their local tectonic setting. The stress regime is strike slip at Arrowsmith 2 well and for an assumed hydrostatic pressure the Kockatea Shale is not close to frictional limits. Minor amounts of methane and trace amounts of short chain alkanes are leaking into deep aquifers pre‐development. In contrast, the stress regime is strike slip/normal at Woodada Deep well and the Kockatea Shale is close to frictional limits. Significant volumes of gas including methane and condensate are leaking into deep aquifers. The sealing capacity of the Kockatea Shale as evidenced by the variation in gas concentration in aquifers at the two sites indicates the formation is sensitive to stress. Additionally given the low permeability of the regional Kockatea Shale seal, it is assumed that at both locations gas leakage is via critically stressed faults. Deep aquifers proximal to the shale gas target are low salinity (<5000 ppm NaCl eq.) at Woodada Deep well and are saline at Arrowsmith 2 well. Based on this assessment, it is suggested that hydraulic fracture stimulation at the Woodada Deep well poses a significant environmental risk.

Skin permeation of oxides of nitrogen and sulfur from short-term exposure scenarios relevant to hazardous material incidents

Permeation of oxides of nitrogen and sulfur gases through skin and the consequences of dermal exposure are still poorly understood. We measured the penetration profile of three common industrial gases through skin, for short-term exposures relevant to HAZMAT scenarios. Time variations of gas concentration, clothing effects, temperature and humidity on epidermal absorption and penetration were assessed. Fabric off-gassing profiles were also investigated. The results show oxides of nitrogen (NO and NO2) at airborne concentrations up to lethal inhalation levels (e.g. 3000 ppm) have little skin penetration ability. Skin absorption and reservoir effects were noted. Skin exposed to SO2 (3000 ppm/30 min) shows negligible skin absorption or penetration. Fabric on skin marginally increased SO2 absorption and subsequent ventilation did not reduce the absorbed fraction. Increased temperature and humidity had limited additional effect on skin penetration. Importantly, clothing demonstrated sink properties, especially for SO2. Short-term skin exposure relevant to accidents will not significantly contribute to body burden. The greatest concern will likely be off-gassing of chemical-laden fabric for asthma suffers. The risk-based management approach is to avoid potential secondary inhalation from fabric off-gassing by removal of outer layer of bulky clothing. Decontamination and moving into an area of enhanced ventilation may also be advised.

Acoustic emission monitoring technology for coal and gas outburst

AbstractIn recent years, with the increase in mining depth and strength, coal‐rock gas dynamic disasters, such as coal and gas outburst, have shown an increasing trend. Acoustic emission (AE) technology has been viewed as a promising method that can effectively forecast coal and gas dynamic disasters. This paper first tests the AE characteristics of coal and rock samples during loading. Then, self‐developed AE continuous monitoring and early warning equipment is used to monitor and predict the coal and gas outburst dynamic disasters on the working face. And it is found that the coal samples primarily show ductile failure, and the AE exhibits the evolutionary characteristics of “rise‐peak‐fall”. The rock samples primarily exhibit brittle failure, and the AE evolution mode is almost no falling stage. Coal and gas outbursts occur after the stress peak. Before coal and gas outbursts occur, there is a clear increasing trend in the AE ahead of the gas concentration variation. When the gas‐bearing coal is damaged by the load, the coal body first breaks due to the stress, and the AE value increases. Then, due to the fracture of the coal body, the crack penetrates, gas rushes out, and the gas concentration increases. The research results can provide an advanced technical method for the monitoring and early warning of coal–rock gas dynamic disasters, and improve the prediction accuracy for dynamic disasters.

The effects of varying gas concentrations and exposure times on colour stability and shelf-life of vacuum packaged beef steaks subjected to carbon monoxide pretreatment

Abstract The aim of this study was to assess the effects of a range of carbon monoxide (CO) concentrations and exposure times on the colour stability and shelf-life of vacuum packaged Longissimus thoracis et lumborum (LTL) beef steaks. Steaks were exposed to five pretreatments: 0 (Control), 0.4, 1, 3 and 5% CO combined with 60% CO2, (balance N2) for 5, 7 or 24 h. They were then vacuum packed and stored at 2 °C for 28 days. The optimum pretreatment was 1% CO for 5 h as this enhanced initial desirable colour yet allowed discolouration to reach unacceptable levels (a* = 12, C* = 16) by the use-by-date (28 days). K/S ratios verified that the optimum CO pretreatment does not mask spoilage. All CO pretreatments had no effect on pH or purge loss (P > 0.05). Reducing the CO concentration and decreasing the exposure time achieved a desirable colour, without masking spoilage, thereby minimizing the processing time and improving the safety of workers.

Spatial-temporal variation features and law of gas concentration in the fully mechanized working face under the condition of intermittent ventilation

Based on the fluid mechanics and mass transfer theory, a mathematical model of the spatial-temporal variation of gas was derived to avoid the gas accident caused by the main fan stopping ventilation under the condition of intermittent ventilation in the tunnel. According to the actual parameters of the tunnel, a numerical calculation model was established. The spatial-temporal variation of gas concentration in the fully mechanized working face under the condition of intermittent ventilation was calculated by using the commercial package Fluent, and the correctness of the calculated results was verified by the actual monitoring data of the mine. Firstly, the gas concentration was calculated under different wind velocities at driving face in coal tunnel, and the result showed that the gas can be carried effectively by the wind when the wind velocity is about 1.8 m/s. Secondly, the distributions of wind velocity and gas concentration at driving face were studied at 1.8 m/s, and the result showed the gas concentration increased gradually with the distance close to the outlet, but the gas concentration almost kept constant at the height of driving face. Thirdly, the distribution of gas concentration was investigated with time after the ventilation was stopped and restarted, respectively. The gas concentration of test point gradually increased with the increment of downtime, when the downtime was 40 min, the gas concentration of test point 3 reached the maximum value. The gas concentration increased gradually and reached the maximum after 10 min of restart, then sharply decreased and kept constant.

Experimental investigation of CO2 injection into coal seam reservoir at in-situ stress conditions for enhanced coalbed methane recovery

CO2 geological sequestration is an effective method to reduce the concentration of CO2 in the atmosphere. The injection of CO2 into CH4-containing coal seams also named CO2-ECBM (CO2 Enhanced Coalbed Methane Recovery), allows the storage of CO2 and the enhancement of CH4 recovery. Due to complex geological environment of the site, dynamic variation of CH4 and CO2 can hardly be monitored in real time during CO2 injection into coal seams. Therefore, this paper conducted experimental studies were carried out on cuboid coal samples with a size of 300 ∗ 70 ∗ 70 mm via a self-developed experimental device which can simulate in-situ stress and temperature conditions. In the experiment, different adsorbed gases (CH4 and CO2) were applied to determine the variation of permeability values under various load stresses and pore pressures. Results proved that the coal had greater adsorption capacity to CO2 than to CH4. The injected CO2 occupied the original adsorption site of CH4, thus leading to the rapid discharge of CH4. Meanwhile, real-time dynamic monitoring was also performed on gas parameters in coal under different gas injection pressures to obtain variation laws of pore pressure, gas flow rate and concentration at the outlet with the increment of injected CO2. The results reveal that with the increase of injected CO2, pore pressure tended to equilibrium while CH4 flow rate and concentration at the outlet gradually fall to zero. Therefore, CO2 injection into the coal mass can effectively improve the recovery of CH4. In addition, variations of gas flow rate and concentration at the outlet with the displacement ratio of gas volume under different gas injection pressures suggested that the enhancement of gas injection pressure boosted discharge efficiency of CH4 from the coal mass and CO2 consumption. Furthermore, inspired by the competition relationship between engineering efficiency and CO2 consumption, we think a reasonable and effective economic cost model can be established as an effective method to guide the selection of gas injection pressure in the future. Hence, the experimental results have guiding significance for better understanding and application of CO2-ECBM technology.

Performance of Pd Doped SnO2 as Sensing Material for Tea Aromatic Chemicals

A facile hydrothermal method was employed to synthesize a Pd doped SnO2 gas sensor. The sensor was experimented with four significant chemicals present in tea at four different operating temperatures. It is observed that the sensor could be used for linalool detection which is an important compound of black tea, responsible for its flavor. The optimum operating temperature is found to be 150 °C at which the sensor showed most favorable sensitivity, response time, and recovery time. Extensive experiments were carried out with different concentrations of linalool gas and the resistance variation of the sensor was observed with variation in gas concentration. The physical characteristics of the sensor were comprehended via X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscopy, and atomic force microscopy analysis.

Photosynthetic and Lipogenic Response Under Elevated CO2 and H2 Conditions—High Carbon Uptake and Fatty Acids Unsaturation

Microalgae are some of the most versatile organisms having ability to grow in diverse conditions and utilize both organic and inorganic carbon sources. Microalgal photosynthesis can be employed to transform carbon dioxide (CO2) into essential bioactives and photofuels. In this study microalgae are grown under modified headspace gas compositions resembling the industrial gaseous effluents. Four experimental variations with CO2 + H2 (1:1 V/V), CO2, H2 and Air as the headspace gas were evaluated to determine the photosynthetic efficiency and bioactives production of microalgae. This study reports an enhancement in quantum yield (Fv/Fm: 0.77) and CO2 biosequestration rate (0.39 g.L-1.d-1) under CO2 + H2 headspace gas composition compared to the other experimental variations. The chemoselective functioning of Rubisco under varying gas concentrations was determined, where elevated CO2 conditions negates the oxygenase activity under a high CO2/O2 ratio which enabled higher CO2 sequestration. The enhanced CO2 sequestration and altered redox conditions under the monophasic operation have also led to a higher average degree of unsaturation and carbon chain length of the fatty acids produced. This study provides an approach to augment photosynthetic efficiency and lipogenesis through non-genetic modifications along with the feasibility to cultivate microalgae in integration with industrial flue gases. Exploiting the true potential of microalgae would provide sustenance from climatic changes and environmental pollution while concurrently producing biobased products analogous to the fossil-derived products.

Multi-model event attribution of the summer 2013 heat wave in Korea

Abstract To assess the anthropogenic influence on the summer 2013 heat wave in Korea, this study employed a fraction of attributable risk (FAR) approach to three Atmospheric General Circulation Models (AGCMs) with a large ensemble simulation, participating in the C20C+ Detection and Attribution Project. Monthly and daily temperatures were compared between two experiments. The real world (ALL) experiments were simulated under the observed variations in sea surface temperature, sea ice, greenhouse gas, and aerosol concentrations, while the counterfactual world (NAT) experiments were performed under adjusted boundary conditions by removing anthropogenic warming and with preindustrial levels of greenhouse gases and aerosols. Results from the three AGCMs consistently show that anthropogenic influences had an important role in the extreme heat event over Korea, increasing the chance of the occurrence of extreme warming in summer mean temperature as observed in 2013 by at least 20 times, which supports results from the Coupled Model Intercomparison Project Phase 5 (CMIP5) coupled GCMs (CGCMs). A comparison of individual CMIP5 CGCMs suggests that inter-model difference in FAR values is highly correlated with the amplitude of surface warming centered over Korea, which is also supported by the three AGCMs. Further analysis of individual forcing experiments suggests that the inter-model difference in the regional surface warming is closely linked to the model's response to the aerosol forcing, with stronger influence than that of greenhouse gas forcing. Anthropogenic influences also result in a 5–6 times greater likelihood of extreme daily heat events as observed in 2013, which supports a robust mean-extreme relation in the attribution of extreme heat waves. Generally good agreement between AGCM and CGCM results increases the robustness of the conclusion of anthropogenic influences on the summer 2013 Korean heat wave.

Agricultural ammonia emissions in China: reconciling bottom-up and top-down estimates

Abstract. Current estimates of agricultural ammonia (NH3) emissions in China differ by more than a factor of 2, hindering our understanding of their environmental consequences. Here we apply both bottom-up statistical and top-down inversion methods to quantify NH3 emissions from agriculture in China for the year 2008. We first assimilate satellite observations of NH3 column concentration from the Tropospheric Emission Spectrometer (TES) using the GEOS-Chem adjoint model to optimize Chinese anthropogenic NH3 emissions at the 1∕2° × 2∕3° horizontal resolution for March–October 2008. Optimized emissions show a strong summer peak, with emissions about 50 % higher in summer than spring and fall, which is underestimated in current bottom-up NH3 emission estimates. To reconcile the latter with the top-down results, we revisit the processes of agricultural NH3 emissions and develop an improved bottom-up inventory of Chinese NH3 emissions from fertilizer application and livestock waste at the 1∕2° × 2∕3° resolution. Our bottom-up emission inventory includes more detailed information on crop-specific fertilizer application practices and better accounts for meteorological modulation of NH3 emission factors in China. We find that annual anthropogenic NH3 emissions are 11.7 Tg for 2008, with 5.05 Tg from fertilizer application and 5.31 Tg from livestock waste. The two sources together account for 88 % of total anthropogenic NH3 emissions in China. Our bottom-up emission estimates also show a distinct seasonality peaking in summer, consistent with top-down results from the satellite-based inversion. Further evaluations using surface network measurements show that the model driven by our bottom-up emissions reproduces the observed spatial and seasonal variations of NH3 gas concentrations and ammonium (NH4+) wet deposition fluxes over China well, providing additional credibility to the improvements we have made to our agricultural NH3 emission inventory.

Stable LSM/LSTM bi-layer interconnect for flat-tubular solid oxide fuel cells

A bi-layer interconnect with La0.8Sr0.2MnO3 and La0.4Sr0.6Ti0.6Mn0.4O3 (LSM/LSTM) is applied to anode-supported button cells and flat-tubular cells. Using a button cell, SEM images and gas permeation tests confirm that the bi-layer possesses a dense microstructure. The area specific resistance (ASR) of the LSM/LSTM remains nearly constant under oxidizing/reducing atmospheres with varying gas concentrations. For comparison, an LSM/LST with the same thickness is prepared; an increase in the ASR is observed as the concentration of H2 feed to the LST side decreases. The difference in the ASR of LSM/LST can be explained by exposure to a relatively high oxygen partial pressure and partial destruction of the interfacial LST layer region where oxygen diffuses from the LSM layer. Flat-tubular cells with the LSM/LSTM bi-layer interconnect achieve a maximum power density (MPD) of 463 mW cm−2 using humidified H2 fuel and air at 800 °C. With decreasing H2 concentration in the fuel, the polarization resistance increases rather than the ohmic resistance, implying that the LSM/LSTM interconnect provides stable conduction property. In comparison with the conventional LSM/LST interconnect cell, it shows improved stability and performance as the concentration of H2 in the fuel decreases.

The PMIP4 contribution to CMIP6 – Part 3: The last millennium, scientific objective, and experimental design for the PMIP4 &amp;lt;i&amp;gt;past1000&amp;lt;/i&amp;gt; simulations

Abstract. The pre-industrial millennium is among the periods selected by the Paleoclimate Model Intercomparison Project (PMIP) for experiments contributing to the sixth phase of the Coupled Model Intercomparison Project (CMIP6) and the fourth phase of the PMIP (PMIP4). The past1000 transient simulations serve to investigate the response to (mainly) natural forcing under background conditions not too different from today, and to discriminate between forced and internally generated variability on interannual to centennial timescales. This paper describes the motivation and the experimental set-ups for the PMIP4-CMIP6 past1000 simulations, and discusses the forcing agents orbital, solar, volcanic, and land use/land cover changes, and variations in greenhouse gas concentrations. The past1000 simulations covering the pre-industrial millennium from 850 Common Era (CE) to 1849 CE have to be complemented by historical simulations (1850 to 2014 CE) following the CMIP6 protocol. The external forcings for the past1000 experiments have been adapted to provide a seamless transition across these time periods. Protocols for the past1000 simulations have been divided into three tiers. A default forcing data set has been defined for the Tier 1 (the CMIP6 past1000) experiment. However, the PMIP community has maintained the flexibility to conduct coordinated sensitivity experiments to explore uncertainty in forcing reconstructions as well as parameter uncertainty in dedicated Tier 2 simulations. Additional experiments (Tier 3) are defined to foster collaborative model experiments focusing on the early instrumental period and to extend the temporal range and the scope of the simulations. This paper outlines current and future research foci and common analyses for collaborative work between the PMIP and the observational communities (reconstructions, instrumental data).