Simplified Mechanism Research Articles

Bacteria-Triggered Solar Hydrogen Production via Platinum(II)-Tethered Chalcogenoviologens.

Multifunctional solar energy conversion offers a feasible strategy to solve energy, environmental and water crises. Herein, a series of platinum(II)-tethered chalcogenoviologens (PtL+ -EV2+ , E=S, Se, Te) is reported, which integrate the functions of photosensitizer, electron mediator and catalyst. PtL+ -EV2+ (particularly for PtL+ -SeV2+ )-based one-component solar H2 production could be triggered not only by EDTA, but also by facultative anaerobic and aerobic bacteria relying on a simplified mechanism, along with efficient antibacterial activities. In addition, by using real pool water, PtL+ -SeV2+ achieved multiple functions, including H2 production, antibacterial action and acid removal, which supplied a new strategy to solve various problems in real life via a single system.

Numerical simulation of fluidized bed pyrolysis under a simplified comprehensive multistep kinetic mechanism: Effects of particle size and fluidization velocity

This study simplified a comprehensive multistep kinetic mechanism of fast biomass pyrolysis in a fluidized bed reactor (involving dense and dilute flows). A wide range of bioparticle sizes (0.2–2.0 mm) was investigated under four fluidization velocities (0.1–0.65 m/s). A multifluid model integrated with heterogeneous chemical reactions was developed to simulate fast biomass pyrolysis in a two-dimensional computational domain. The simplified multistep comprehensive reaction corresponded well to the product yield and composition data previously obtained through experimental pyrolysis. Most of the pyrolysis reactions occurred in the dense region and suddenly reduced the reaction rate in the freeboard. The relatively small size of the bioparticles facilitated their removal from the reactor, improved mixing performance, and resulted in a larger gas–bioparticle heat transfer coefficient and a faster reaction rate. However, particles that were excessively small (0.2 mm) shortened the bioparticle residence time substantially; this resulted in a considerable increase in the solid residue yield, the consumption of slightly more heat for pyrolysis, and further reduction in pyrolysis efficiency. Higher fluidization velocity led to shorter bioparticle residence time and improved the mixing performance of the solids, with a weak effect on the gas–bioparticle heat transfer coefficient. With a broader distribution region, this high velocity reduced the reaction rate slightly and increased the specific heat for pyrolysis substantially (from ∼879 kJ/kg to ∼4043 kJ/kg), thus reducing the pyrolysis efficiency (from 92.8% to 94.3% to 74.4%–76.9%).

Self-aeration development and fully cross-sectional air diffusion in high-speed open channel flows

Self-aeration in open channel flows occurs owing to free surface air entrainment. Self-aeration development and fully cross-sectional distribution of air concentration are not thoroughly understood. In the present study, an analytical solution for the averaged cross-sectional air concentration in the gradually varying region is established using a simplified mechanism of free surface air entrainment. For a fully cross-sectional distribution of air concentration affected by the channel bottom, a model of a diffusion region without wall restraint is proposed, and two situations are classified based on averaged cross-sectional air concentration. Good agreement between measured data and calculations is obtained, and the computational accuracy of the air concentration distribution near the wall is improved. The results reveal that the channel slope determines the air entrainment quantity, while water flow discharge determines the self-aeration evolution distance. The solutions for the averaged cross-sectional air concentration and the effect of the bottom wall on air diffusion promote air–water flow applications in hydraulic engineering practices.

A Simplified Jet Fuel Oxidation Mechanism for Numerical Simulation of Ignition Process

A Simplified Jet Fuel Oxidation Mechanism for Numerical Simulation of Ignition Process

WebStart WEPS: WEPS with Remote Data Access and Cloud-Computing Functionality

HighlightsWebStart WEPS is a Java WebStart enabled browser-accessible version of WEPS.This model-as-a-service cloud-based system provides remote access to model inputs and remote model execution.Default QuickPlot reports are provided to quickly visualize model results.MapViewer revisions are provided to improve map-based site selections.Abstract. The Wind Erosion Prediction System (WEPS) is a physical process-based wind erosion model developed by the USDA Agricultural Research Service (USDA-ARS). WEPS simulates daily climate and management-driven changes to the surface, vegetation, and soil. It estimates erosion losses when surface conditions and wind speeds are sufficient for soil movement. WEPS was released in 2010 to the USDA Natural Resources Conservation Service (USDA-NRCS) for assisting land managers in controlling wind erosion, establishing field-level plans for soil conservation, and determining wind erosion susceptibility as a part of national conservation programs to conserve the soil resource. The WEPS interface allows easy user access to national-scale input data. Four primary inputs are required to set up and execute a WEPS run: (1) field dimensions; (2) field location, which automatically determines applicable local climate data; (3) a representative soil; and (4) time series of management practices. These inputs require access to a significant amount of data, which are typically stored locally; however, maintaining these data on every computer running WEPS and keeping them current were problematic for the NRCS. To address these concerns, remote access functionality was incorporated into WEPS to deliver climate and wind data, as well as soil, operation, crop/residue, and management (a date-sequenced list of management operations) records. In addition, WebStart WEPS also features the option of running WEPS components remotely “in the cloud” as web services. The Java WebStart framework provides a simplified delivery mechanism to users’ computers and offers automatic updating capability. Keywords: Cloud services, CSIP, Erosion, Java WebStart, Modeling, WEPS, Wind erosion.

ЕЛЕКТРОННЕ УРЯДУВАНН В УКРАЇНІ: СПЕЦИФІКА РОЗВИТКУ В УМОВАХ КРИЗИ

The article considers the development of e-government in Ukraine during the military aggression in our country and under the influence of such a disease as COVID-19, because due to the mass pandemic many institutions that provide necessary administrative and public services to citizens were forced to go online regime, which was a great impetus for the spread of digitalization and modernization of legislation, and due to the imposition of martial law, the provision of some administrative services was suspended and access to registers was limited, so the question arises to study this issue. We have studied the legal framework for the development of e-government in Ukraine. The essence, features and advantages of functioning of e-government technologies are also analyzed. The current state of e-government in Ukraine in the period from 2016 to the present is determined separately, namely the compliance of Ukrainian legislation with the objectives of e-government development. Consideration in the work of the policy, goals and objectives of the newly created body in this area, namely the Ministry of Digital Transformation of Ukraine, is relevant. We also considered the policy of the newly formed government regarding the introduction of "State in a smartphone" through the use of such a mobile application as "Action", which has recently become very popular due to the simplified mechanism of providing administrative services to citizens without leaving home. Through the prism of European experience, the introduction of such an application as "Action at home", which facilitates the control of people who are already ill or in self-isolation. The issue of obtaining a certificate of internally displaced person status was considered separately, which is very important for people who have been forced to leave their homes and need protection from the state. Our research shows that even the impact of emergencies can lead to positive developments in the country, and after reading this paper you will understand that the government's plans to develop e-government are quite ambitious, but at the same time promising. Therefore, in the near future, most public services will be available using only a smartphone or computer, and due to hostilities, some services have been restricted but are temporary and in constant motion.

Effect of Pre-Injection on Combustion and Emission Characteristics of a Diesel Engine Fueled with Diesel/Methanol/n-Butanol Blended Fuel

In this study, the combustion and emission characteristics of a diesel/methanol/n-butanol blended fuel engine with different pre-injection timings and pre-injection mass ratios were investigated by a computational fluid dynamics (CFD) model. The CFD model was verified by the measured results and coupled with a simplified chemical kinetics mechanism. Firstly, the corresponding three-dimensional CFD model was established by CONVERGE software and the CHEKMIN program, and a chemical kinetic mechanism containing 359 reactions and 77 species was developed. Secondly, the combustion and emission characteristics of the diesel engine with different diesel/methanol/n-butanol blended fuels were analyzed and discussed. The results showed that increases in the pre-injection timing and the pre-injection mass ratio could increase cylinder pressure and cylinder temperature and decrease soot, HC, and CO emissions. At 100% load, the maximum cylinder pressures at the start of pre-injection timing from −15 °CA to −45 °CA, were 7.71, 9.46, 9.85, 9.912, and 9.95 MPa, respectively. The maximum cylinder pressures at pre-injection fuel mass ratios from 0.1 to 0.9 were 7.98, 9.10, 9.96, 10.52, and 11.16 MPa, respectively. At 50% load, with increases of the pre-injection timing and pre-injection fuel mass ratio, the soot emission decreased by 7.30%, 9.45%, 27.70%, 66.80%, 81.80% and 11.30%, 20.03%, 71.32%, 83.80%, 93.76%, respectively, and CO emissions were reduced by 5.77%, 12.31%, 22.73%, 53.59%, 63.22% and 8.29%, 43.97%, 53.59%, 58.86%, 61.18%, respectively. However, with increases of the pre-injection timing and pre-injection mass ratio, NOx emission increased. In addition, it was found that the optimal pre-injection timing and optimal pre-injection mass ratio should be −30 °CA and 0.5, respectively. Therefore, through this study we can better understand the potential interaction of relevant parameters and propose pre-injection solutions to improve combustion and emission characteristics.

Construction of simplified combustion mechanism of diesel from direct coal liquefaction-PODE3

DDCL (Diesel from Direct Coal Liquefaction) and PODEn (Polyoxymethylene Dimethyl Ethers) are alternative fuels commonly used for Diesel engines. Their blend has close cetane number to diesel fuel. N-dodecane and decalin were selected as model fuels of DDCL. Based on the decoupling method, initial simplified combustion mechanism reaction paths were constructed, and the sensitive reaction rate parameters were optimized by PSO (Particle Swarm Optimization). Then the simplified combustion mechanism of DDCL was constructed by combining the mechanisms of the two fuels, and the NOx mechanism was combined to form the DDCL-PODE3-NOx mechanism. Moreover, the prediction performance of the simplified mechanism was verified via JSR (Jet Stirred Reactor) test, and the results proved that it can provide a reliable prediction of the ignition delay time and species concentration distribution. Eventually, the DDCL simplified mechanism contains 156 components and 617 reactions. The PODE3 mechanism contains 149 components and 597 reactions, and the DDCL-PODE3-NOx simplified mechanism contains 171 components and 642 reactions. Constructing fuel combustion mechanism is the basis of fuel combustion research. Most significantly, the simplified combustion mechanism shows excellent prediction in the basic combustion test data.

Chemical Kinetic Study on Dual-Fuel Combustion: The Ignition Properties of n-Dodecane/Methane Mixture

The natural gas (NG)/diesel dual-fuel engine has attracted extensive attention in recent years, and the influence of ignition delay on the engine is very important. Therefore, the research on the ignition delay of NG/diesel dual fuel is of great significance. In this work, a simplified n-dodecane mechanism was used to study the effect of methane mixture ratio on the n-dodecane ignition process. The results showed that the ignition delay time increased with the increase of methane content by changing the mixing ratio of methane and n-dodecane. However, the effect of methane on the ignition delay time gradually decreases when the content of the n-dodecane mixing ratio is greater than 50%. It was also found that with the increase of n-dodecane content, the reduction degree of the ignition delay time of the whole reaction system decreased and the negative temperature coefficient (NTC) behavior increased. Moreover, when the initial pressure increased from 20 bar to 60 bar, the thermal effect of methane also increases from 7.03% to 9.55%. The relationship between ignition characteristics of methane-n-dodecane and temperature was studied by changing the initial temperature. Furthermore, the evolution of species in the ignition process of the whole reaction system was analyzed, and the decomposition of n-dodecane first occurs in the reaction n-C12H26 + O2 = R + HO2 to form R and free radicals; however, the reaction CH4 + OH = CH3 + H2O dominates with the increase of the methane mixing ratio and inhibits the ignition process. Through the analysis of reaction paths, sensitivity, and rates of production and consumption of methane/n-dodecane, it was explained how n-dodecane accelerates methane ignition through the rapidly formed free radicals.

Characterization and management of human-wildlife conflicts in mid-hills outside protected areas of Gandaki province, Nepal.

With the intent to better management human wildlife conflict (HWC) and wildlife conservation in mid-hills outside protected areas of Gandaki province, Nepal, we analyzed the patterns and drivers of HWC. Using data collected from literature, government records and questionnaire survey, we investigated temporal, seasonal and spatial distribution of human casualties caused by wildlife attacks. We also appraised the perception of local people towards wildlife conservation. We have recorded 77 cases (69 human injuries and 8 mortalities) during the period of nine year between 2011 and 2019. The number of wildlife attacks increased over this period. Wildlife attacks were more frequent in winter with 50% (42) of attacks occurred between September and December. Common leopard (Panthera pardus) and Himalayan black bear (Ursus thibetanus laniger) were the major species involved in these conflicts. Common leopard was the most feared species that causes highest number of human mortalities (87%, n = 67); the most severe type of HWC outcome. Forty-eight percent (n = 37) attacks were reported at human settlement areas followed by 27% attacks in agriculture land (n = 21) and 24% (n = 19) in forest. Generalized linear model analysis on spatial variables showed that the probability of human attacks increases with decreasing elevation (β = -0.0021, Z = -1.762, p = 0.078) and distance from the forest (β = -0.608, Z = -0.789, p = 0.429). We recommend to decrease habitat degradation / fragmentation, carry out habitat management program within forest to increase prey availability to decrease the wildlife invasion into human settlement area, and decrease dependency of people on forest resources by providing alternative livelihood opportunities. Simplified relief fund distribution mechanism at local level also helps alleviate the impact of HWC. The knowledge obtained by this study and management measures are important for better human-wildlife co-existence.

Development of a Reduced Methane-Hydrogen-Polyoxymethylene Dimethyl Ether Mechanism under Engine-Relevant Conditions.

Polyoxymethylene dimethyl ethers (PODEn) have a high cetane number and a high oxygen content, which can effectively reduce the soot emission. In this study, PODE3, methane, and hydrogen were used as the characterization fuel. First, the detailed reaction mechanism of PODE3 and GRI-Mech 3.0 was reduced under engine-relevant conditions by using the reduced methods of the direct relation graph, the directed relation graph with error propagation, the sensitivity analysis, and the reaction pathway analysis. Then, the simplified PODE3 and methane–hydrogen mechanism were coupled and optimized. Finally, the simplified chemical kinetics mechanism of methane–hydrogen–PODE3 (67 species, 260 reactions) was developed. After that, the methane–hydrogen–PODE3 mechanism for methane/hydrogen/PODE3 blend combustion was established, and experimental verification was performed against ignition delay times, laminar flame speeds, and premixed flame species profiles, which showed a good agreement between the predicted and experimental data. Finally, the current mechanism was found to have high reliability and can be coupled to computational fluid dynamics.

Nanoscale Ag/WO3 Multilayered Fabry–Perot Cavities for Colorimetric NO2 Sensing

High-performance gas sensors with low operating temperatures are of emerging research interest. They do not require heaters, thus guaranteeing cost-effectiveness and low power consumption. This is a study to demonstrate the possibility of fabricating a high-performance sensor through a simplified mechanism based on the surface property changes of a Fabry–Perot cavity. Here, the upper metal reacts independently, allowing accurate analyses to be performed while minimizing errors due to external factors. The proposed sensor rapidly responds to corrosive gases; it shifts the absorption wavelength by over 45 nm, that is, from 552 to 597 nm within 15 min at room temperature, significantly changes the color from purple to blue, and can be fabricated in bulk using conventional electron-beam physical vapor deposition. NO2 gas experiments verify the sensor’s superior performance and productivity potential, demonstrating its applicability in urban areas and factories.

Asymptotic analysis of cool-flame propagation in mixtures of an n-alkane, oxygen, and nitrogen

A simplified chemical-kinetic cool-flame mechanism for n-alkanes has recently been developed and applied to the description of quasi-steady droplet combustion. Chemistry of this same general type can support premixed laminar cool-flame deflagrations. The present contribution derives the structure of the associated freely propagating cool premixed flame controlled by the low-temperature chemistry and develops formulas for calculating the corresponding laminar burning velocity. Application of activation-energy asymptotics reveals finite-rate chemistry, among essential intermediates (with concentrations so small that associated heat release is negligible), occurring throughout the preheat zone. There is leakage of both fuel and oxygen through the thin heat-release zone, with zones of consumption of an intermediate species on each side of the heat-release zone, thicker than that zone but still thin compared with the preheat-zone thickness. Predicted laminar burning velocities are compared with recently reported measurements for n-dodecane, performed in a newly designed high-pressure droplet ignition apparatus, resulting in reasonable agreement after account is taken of the process of insertion of the droplet into the furnace and of the velocity of the buoyant plume present in the experiment.

Development and verification of simplified methane/dimethyl ether mechanism for micro-combustion

In this work, a simplified mechanism for simulating methane/dimethyl ether micro-flames is developed by validating the flame speed and ignition delay time. Towards this goal, DRGEPSA is used to simplify the pure dimethyl ether mechanism proposed by Zhao. Then the simplified mechanism is coupled with the existing pure methane mechanism (kee-58 mechanism) to obtain the blended fuel mechanism. The sensitivity analysis indicates that the chemical reaction HCOOH = HCO + OH is most beneficial to the optimization of the blended fuel mechanism. By adjusting this reactions reaction rate, the dynamic characteristics and applicability of the blended fuel mechanism in the numerical simulation are adjusted, resulting in a simplified mechanism containing 25 species and 96 chemical reactions. The predicted ignition delay time and laminar flame speed are well matched with the experimental results under certain conditions, showing the capability of this simplified mechanism in describing the combustion characteristics. Finally, this mechanism is applied to predict the transition rules of flame structure, flame location, and blowout limit of methane/dimethyl ether flames under micro-scale conditions using a three-dimensional model. A good agreement between calculations and experimental measurements is achieved, demonstrating the reliability of the simplified mechanism developed in the present work.

Evaluation Model for Fast Convective Heat Transfer Characteristics of Thermal Cracked Hydrocarbon Fuel Regenerative Cooling Channel in Hydrocarbon-Fueled Scramjet

• A fast flow and heat transfer evaluation model with simplified endothermic pyrolysis was established. • Influence of inlet fuel mass flow on flow and heat transfer characteristics was studied. • Influence of two types heat flux on flow and heat transfer characteristics was studied. • An inner fuel temperature inside cooling channel detective method was derived from above results. Regenerative cooling is critical for hypersonic propulsion systems, wherein the flow and heat transfer characteristics of the hydrocarbon fuel in the cooling channel are crucial. The most commonly used existing evaluation models for flow and heat transfer characteristics use one-step overall reaction endothermic pyrolysis; however, they are limited to mildly cracked hydrocarbon fuel working conditions. To quickly evaluate the flow and heat transfer characteristics of hydrocarbon fuel under both mild- and heavy-cracking conditions, a quasi-one-dimensional model was established in this study; considering 18 species and 24 reactions, and a simplified mechanism of n-decane. The flow and heat transfer characteristics under different cooling channel lengths and heat fluxes were studied. The results show that the proposed model has fast flow and heat transfer characteristics evaluation capability, and small persistent errors. Furthermore, the calculation results under different inlet fuel mass flow and heat flux working conditions showed that the hydrocarbon fuel flow and heat transfer characteristics vary with the fuel mass flow and heat flux, which can enhance both heat transfer and deterioration. The influence of the heat flux can be used to measure the fuel temperature inside the channel.

Research on Adaptive Hybrid Energy Consumption Model Based on Data Driven under Variable Working Conditions

As to the nonlinear and time-varying problems of the energy consumption model, this paper proposes an adaptive hybrid modeling method. Firstly, the recursive least squares algorithm with adaptive forgetting factor based on fuzzy algorithm and recursive least squares algorithm is used to identify the simplified mechanism energy consumption model, which solves the data saturation phenomenon and the weights of the “old and new” data during the online identification process and guarantees the adaptability of the mechanism model. Secondly, because there is a deviation between the identified model and the simplified mechanism energy consumption model, the deviation compensation model of mechanism model is established through kernel partial least squares algorithm and the model updating strategy with sliding window, which is used to update the deviation compensation model, and then the adaptive hybrid model is established by combining with the mechanism model identified online and updated deviation compensation model. Finally, the effectiveness, generalization and adaptability of the model are verified by the actual operating data of a single working condition and variable working conditions. And comparing with the mechanism model and the data model, The comparison results show that the adaptive hybrid model has higher calculation accuracy with adaptation.

Who are the celebrities? Identifying vital users on Sina Weibo microblogging network

Vital node detection in a social graph is a long-standing challenge for understanding the exchange, sharing, and dissemination of information on social media. As one of the most popular social media platforms in China, the Sina Weibo microblogging website has millions of users. Of these, vital users play an important role in impacting other common users’ online behaviors, promoting online information dissemination, and leading public opinion trends. Therefore, it is of theoretical and practical interest to study the identification of vital users on the Sina Weibo network. In contrast to traditional approaches, after investigating the unique characteristics of the vital users in the Sina Weibo network, we proposed an end-to-end computational model based on the deep graph neural network. The proposed model introduced a simplified graph attention mechanism to incorporate the information of both the follower and followee networks of users, which can maintain a relatively low computational cost compared with the traditional GAT model but at the same time maintain comparable detection accuracy. The comparison experiments between the proposed model, classic node ranking methods, and graph embedding-based classifiers verified that the proposed model has the best accuracy in detecting vital users in the Sina Weibo network.

Effects of Different Injection Strategies on Combustion and Emission Characteristics of Diesel Engine Fueled with Dual Fuel

In this work, an effective numerical simulation method was developed and used to analyze the effects of natural gas mixing ratio and pilot-main injection, main-post injection, and pilot-main-post injection strategies on the combustion and emission characteristics of diesel engine fueled with dual fuel. Firstly, the one-dimensional calculation model and three-dimensional CFD model of the engine were established by AVL-BOOST and AVL-Fire, respectively. In addition, the simplified chemical kinetics mechanism was adopted, which could accurately calculate the combustion and emission characteristics of the engine. The results show that the cylinder pressure and heat release rate decrease with the increase of the natural gas mixing ratio and the NOx emission is reduced. When the NG mixing ratio is 50%, the NOx and CO emission are reduced by 47% and 45%, respectively. When the SODI3 is 24 °CA ATDC, the NOx emission is reduced by 29.6%. In addition, with suitable pilot-main injection and pilot-main-post injection strategies, the combustion in the cylinder can be improved and the trade-off relationship between NOx and soot can be relaxed. Thus, the proper main-post injection strategy can improve the combustion and emission characteristics, especially the reduction in the NOx and CO emissions.

Development and Verification of the New Simplified Mechanism for CH4/O2/CO2 Laminar Premixed Flame under High Pressure.

To study the laminar premixed flame characteristics of methane under an O2/CO2 atmosphere in high pressure, a new simplified chemical mechanism (44 steps and 19 species) was extracted from the GRI-Mech 3.0 mechanism. The sensitivity coefficient analysis method is used to retain the elementary reactions that have great influence on the target parameters and remove other secondary elementary reactions. Meanwhile, the closeness of the simplified mechanism initially obtained was verified. The results of the laminar burning velocities, the distribution of the main species, and the ignition delay time were compared between the two mechanisms for the premixed flame and the ignition process. Overall, the simplified mechanisms performed fairly well over a wide range of pressure, equivalence ratio, and fuel mixture composition.

A Novel Single-Loop Mechanism and the Associated Cylindrical Deployable Mechanisms

This paper presents a new type of 2-DOF single-loop mechanism inspired by the Sarrus mechanism, and it utilizes this mechanism to construct 2-DOF cylindrical deployable mechanisms. First, the motion pattern of the single-loop mechanism is analyzed utilizing screw theory. According to the structural symmetries, the cylindrical deployable mechanisms are constructed through the linear pattern combination and circular pattern combination of the single-loop mechanisms. After the geometrical analysis and interference condition analysis, the axial, circumferential and area magnification ratios are defined and, furthermore, applied to the parameter optimization of the deployable mechanisms, forming an example surface. Finally, a simplified 1-DOF single-loop mechanism is derived from the proposed 2-DOF mechanism, which is used to construct 1-DOF cylindrical deployable mechanisms with singular free workspaces.