Improving the specific,technical,economic,and environmental characteristics of piston engines(ICE)operating on alternative gaseous fuels is a pressing task for the energy and mechanical engineering industries.The aim ...Improving the specific,technical,economic,and environmental characteristics of piston engines(ICE)operating on alternative gaseous fuels is a pressing task for the energy and mechanical engineering industries.The aim of the study was to optimize the parameters of the ICE working cycle after replacing the base fuel(propane-butane blend)with syngas from wood sawdust to improve its technical and economic performance based on mathematical modeling.The modeling results were verified through experimental studies(differences for key parameters did not exceed 4.0%).The object of the study was an electric generator based on a single-cylinder spark ignition engine with a power of 1 kW.The article describes the main approaches to creating a mathematical model of the engine working cycle,a test bench for modeling verification,physicochemical properties of the base fuel(propane-butane blend),and laboratory syngas.It was shown that replacing the fuel from a propane-butane blend to laboratory syngas caused a decrease in engine efficiency to 33%(the efficiency of the base ICE was 0.179 vs.the efficiency of 0.119 for the converted ICE for the 0.59 kW power mode).Engine efficiency was chosen as the key criterion for optimizing the working cycle.As a result of optimization,the efficiency of the converted syngas engine was 6.1%higher than that of the base engine running on the propane-butane blend,and the power drop did not exceed 8.0%.Thus,careful fine-tuning of the working cycle parameters allows increasing the technical and economic characteristics of the syngas engine to the level of ICEs running on traditional types of fuel.展开更多
The objectives of this study were to explore the spatial distribution of soil available microelements and to provide a firm foundation for scientifically formulated fertilizer. 1 076 soil samples were collected from P...The objectives of this study were to explore the spatial distribution of soil available microelements and to provide a firm foundation for scientifically formulated fertilizer. 1 076 soil samples were collected from Pinggu County of Beijing, China, and the contents of available Cu, Zn, Fe, and Mn in topsoil （0-20 cm） and subsoil （20-40 cm） were analyzed respectively. Descriptive statistics and geostatistics were used to analyze the data. The mean values of topsoil available Cu, Zn, Fe, and Mn were 1.96, 2.51, 17.32, and 10.91 mg kg^-1, respectively, which were at medium or at slightly above medium level. The topsoil content of the soil available microelements was more than that of subsoil. The result of semivariance analysis showed that the topsoil available Fe and Mn were spatially correlated at a larger distance of 21.6 and 45.3 km, and the available Cu and Zn were at a shorter distance of 3.1 and 2.9 km, respectively. The subsoil spatial correlation distances were obviously different from the topsoil, which were in the order of available Mn 〉 Cu 〉 Zn = Fe. The Kriging method was applied to calculate the unobserved points and was used to generate the contour map. The results showed that the structural factors, such as topology, soil types, and soil properties, were the main factors influencing the spatial distribution of topsoil available Fe and Mn. Topsoil available Cu and Zn contents were mainly affected by land use, and their contents in orchard and in vegetable land were greatly higher than in field. The spatial distribution of subsoil microelements was similar to that of the topsoil, which exhibited vertical distribution patterns. Fertilizer and pesticide application resulted in the higher contents of available Cu and Zn in Pinggu County. The higher content of available Zn is potentially harmful to soil environmental quality, which should be inspected.展开更多
In the electricity market, charging based on the traditional spot electricity price often results in the payment imbalance of electric network, and goes against the development of the power system. So, it is necessary...In the electricity market, charging based on the traditional spot electricity price often results in the payment imbalance of electric network, and goes against the development of the power system. So, it is necessary to modify the spot price. The key of the modification lies in how to calculate the fixed unit transmission cost of each node, that is how to allocate the fixed transmission cost to users.To solve this problem, we develop a power flow tracing algrithm to modify the spot price. We put forward a path searching method based on the graph theory after studying the fundamental principle of power flow tracing and apply the method to the downstream tracing algorithm and upstream tracing algorithm according to the proportional distribution principle. Furthermore, to improve the computational efficiency of the algorithm, we introduce the branch expunction method to optimize the node order. By using the result of power flow tracing to get fixed node transmission cost and introducing it to modify the spot price, we obtain the synthetical price.The application to a 5-bus system prove the algorithm feasible.展开更多
The MARGov Project consisted in strengthening the interaction among the Professor Luiz Saldanha Marine Park stakeholders, and to collaboratively construct, with social and institutional actors, a governance model for ...The MARGov Project consisted in strengthening the interaction among the Professor Luiz Saldanha Marine Park stakeholders, and to collaboratively construct, with social and institutional actors, a governance model for the Marine Park, located in the municipality of Sesimbra （Portugal）. To pursue this goal, a PPGIS （public participation geographic information system） was developed, allowing the interaction, discussion and public participation of the stakeholders and actors involved. This PPGIS emerged as a crowdsourcing tool, with the purpose of assisting the georeferenced contributes from the local users of the Marine Park, regarding several relevant subjects, such as pollution, economic activities, opportunities and threats to the Marine Park, providing visual, analytical, and demonstrative qualities.展开更多
Flame propagation speeds are reported for ammonia/hydrogen/air mixtures with equivalence ratios in the range of 0.5-1.5,preheated gas temperatures ranging from 298 K to 673 K and hydrogen volume fractions of0%,20%,and...Flame propagation speeds are reported for ammonia/hydrogen/air mixtures with equivalence ratios in the range of 0.5-1.5,preheated gas temperatures ranging from 298 K to 673 K and hydrogen volume fractions of0%,20%,and 50%.The measurements were conducted using a Bunsen burner and an optical schlieren system.The results show that the flame propagation speed and combustion stabilities of the premixed gases increase with increasing preheating temperature.The combustion stability is significantly improved under the 20%hydrogen volume fraction condition.For the NH_(3)/H_(2)mixtures with a hydrogen volume fraction of 50%,the flame propagation speed at 673 K with a stoichiometric ratio is approximately 4.85 times that at 298 K.The experimental results show that at 673 K,the flame propagation speed of the NH_(3)/H_(2)/air mixture increases by 7.8times when the hydrogen volume fraction increases from 20%to 80%.The numerical results predicted with the Mei,Shrestha,and Stagni mechanisms are compared with the experimental data.The mechanisms proposed by Shrestha and Stagni overestimate the flame propagation speed,especially at high preheating temperatures.The results predicted with the Mei mechanism are consistent with the available data.The concentrations of OH,H,O and NH_(2)are increased by the hydrogen addition;thus,the ammonia consumption is accelerated.展开更多
Scheduled for an Earth-to-Mars launch opportunity in 2020,the China’s Mars probe will arrive on Mars in 2021 with the primary objective of injecting an orbiter and placing a lander and a rover on the surface of the R...Scheduled for an Earth-to-Mars launch opportunity in 2020,the China’s Mars probe will arrive on Mars in 2021 with the primary objective of injecting an orbiter and placing a lander and a rover on the surface of the Red Planet.For China’s 2020 Mars exploration mission to achieve success,many key technologies must be realized.In this paper,China’s 2020 Mars mission and the spacecraft architecture are first introduced.Then,the preliminary launch opportunity,Earth–Mars transfer,Mars capture,and mission orbits are described.Finally,the main navigation schemes are summarized.展开更多
This paper presents a novel power flow tracing (PFT) algorithm for electric networks with loopflow (ENL)—PFT(EN)L algorithm. During calculating process, the simplified network is obtained using the equivalent node fo...This paper presents a novel power flow tracing (PFT) algorithm for electric networks with loopflow (ENL)—PFT(EN)L algorithm. During calculating process, the simplified network is obtained using the equivalent node for the loopflow part of a network. Graph theory is applied to determining the directed path from any generator-bus to load-buses with the proposed algorithm. Based on the AC load flow, the proportional sharing principle, series theory and the directed paths, the contribution of generators to the line flows and the extraction of loads from the generators can be calculated. The definitions and properties of auto-loopflow-coefficient (ALC) of an ENL are pro-posed. In this paper, two theorems have been proved: one is that the PFTL algorithm is always convergent with the properties of ALC; and the other is that the condition under which the whole contribution of any generator to all loads equals the output of the generator for a lossless ENL will be well satisfied with the PFTL algorithm. The developed algorithm has been tested on a number of test systems and the results show the feasibility and applicability of the approach.展开更多
Autoencoder-based rating prediction methods with external attributes have received wide attention due to their ability to accurately capture users'preferences.However,existing methods still have two significant li...Autoencoder-based rating prediction methods with external attributes have received wide attention due to their ability to accurately capture users'preferences.However,existing methods still have two significant limitations:i)External attributes are often unavailable in the real world due to privacy issues,leading to low quality of representations;and ii)existing methods lack considering complex associations in users'rating behaviors during the encoding process.To meet these challenges,this paper innovatively proposes an inherent-attribute-aware dual-graph autoencoder,named IADGAE,for rating prediction.To address the low quality of representations due to the unavailability of external attributes,we propose an inherent attribute perception module that mines inductive user active patterns and item popularity patterns from users'rating behaviors to strengthen user and item representations.To exploit the complex associations hidden in users’rating behaviors,we design an encoder on the item-item co-occurrence graph to capture the co-occurrence frequency features among items.Moreover,we propose a dual-graph feature encoder framework to simultaneously encode and fuse the high-order representations learned from the user-item rating graph and item-item co-occurrence graph.Extensive experiments on three real datasets demonstrate that IADGAE is effective and outperforms existing rating prediction methods,which achieves a significant improvement of 4.51%~41.63%in the RMSE metric.展开更多
Lithium niobate （LiNbO3） is a useful photonic material for its electro-optic and nonlinear optical properties. In this paper, I will report developments of LiNbO3 based optical devices for fiber communication, inclu...Lithium niobate （LiNbO3） is a useful photonic material for its electro-optic and nonlinear optical properties. In this paper, I will report developments of LiNbO3 based optical devices for fiber communication, including high-performance modulators and high efficiency wavelength converters.展开更多
The optically based technique of electro-optic (EO) sampling has been used for diagnosing the internal high-speed signals of integrated circuits.One of the features that make the EO sampling technique very promising i...The optically based technique of electro-optic (EO) sampling has been used for diagnosing the internal high-speed signals of integrated circuits.One of the features that make the EO sampling technique very promising is a minimal probe: the EO sampling technique does not require an electrode and ground plane incorporated as part of a probe so that, compared with conventional metal probes, the invasiveness of an EO probe is minimal.展开更多
基金the Ministry of Science and Higher Education of the Russian Federation(Ural Federal University Program of Development within the Priority-2030 Program)is gratefully acknowledged.
文摘Improving the specific,technical,economic,and environmental characteristics of piston engines(ICE)operating on alternative gaseous fuels is a pressing task for the energy and mechanical engineering industries.The aim of the study was to optimize the parameters of the ICE working cycle after replacing the base fuel(propane-butane blend)with syngas from wood sawdust to improve its technical and economic performance based on mathematical modeling.The modeling results were verified through experimental studies(differences for key parameters did not exceed 4.0%).The object of the study was an electric generator based on a single-cylinder spark ignition engine with a power of 1 kW.The article describes the main approaches to creating a mathematical model of the engine working cycle,a test bench for modeling verification,physicochemical properties of the base fuel(propane-butane blend),and laboratory syngas.It was shown that replacing the fuel from a propane-butane blend to laboratory syngas caused a decrease in engine efficiency to 33%(the efficiency of the base ICE was 0.179 vs.the efficiency of 0.119 for the converted ICE for the 0.59 kW power mode).Engine efficiency was chosen as the key criterion for optimizing the working cycle.As a result of optimization,the efficiency of the converted syngas engine was 6.1%higher than that of the base engine running on the propane-butane blend,and the power drop did not exceed 8.0%.Thus,careful fine-tuning of the working cycle parameters allows increasing the technical and economic characteristics of the syngas engine to the level of ICEs running on traditional types of fuel.
基金Beijing Educatinal Com-mittee Technological Development Program Key Item (KM-200510020006)
文摘The objectives of this study were to explore the spatial distribution of soil available microelements and to provide a firm foundation for scientifically formulated fertilizer. 1 076 soil samples were collected from Pinggu County of Beijing, China, and the contents of available Cu, Zn, Fe, and Mn in topsoil （0-20 cm） and subsoil （20-40 cm） were analyzed respectively. Descriptive statistics and geostatistics were used to analyze the data. The mean values of topsoil available Cu, Zn, Fe, and Mn were 1.96, 2.51, 17.32, and 10.91 mg kg^-1, respectively, which were at medium or at slightly above medium level. The topsoil content of the soil available microelements was more than that of subsoil. The result of semivariance analysis showed that the topsoil available Fe and Mn were spatially correlated at a larger distance of 21.6 and 45.3 km, and the available Cu and Zn were at a shorter distance of 3.1 and 2.9 km, respectively. The subsoil spatial correlation distances were obviously different from the topsoil, which were in the order of available Mn 〉 Cu 〉 Zn = Fe. The Kriging method was applied to calculate the unobserved points and was used to generate the contour map. The results showed that the structural factors, such as topology, soil types, and soil properties, were the main factors influencing the spatial distribution of topsoil available Fe and Mn. Topsoil available Cu and Zn contents were mainly affected by land use, and their contents in orchard and in vegetable land were greatly higher than in field. The spatial distribution of subsoil microelements was similar to that of the topsoil, which exhibited vertical distribution patterns. Fertilizer and pesticide application resulted in the higher contents of available Cu and Zn in Pinggu County. The higher content of available Zn is potentially harmful to soil environmental quality, which should be inspected.
文摘In the electricity market, charging based on the traditional spot electricity price often results in the payment imbalance of electric network, and goes against the development of the power system. So, it is necessary to modify the spot price. The key of the modification lies in how to calculate the fixed unit transmission cost of each node, that is how to allocate the fixed transmission cost to users.To solve this problem, we develop a power flow tracing algrithm to modify the spot price. We put forward a path searching method based on the graph theory after studying the fundamental principle of power flow tracing and apply the method to the downstream tracing algorithm and upstream tracing algorithm according to the proportional distribution principle. Furthermore, to improve the computational efficiency of the algorithm, we introduce the branch expunction method to optimize the node order. By using the result of power flow tracing to get fixed node transmission cost and introducing it to modify the spot price, we obtain the synthetical price.The application to a 5-bus system prove the algorithm feasible.
文摘The MARGov Project consisted in strengthening the interaction among the Professor Luiz Saldanha Marine Park stakeholders, and to collaboratively construct, with social and institutional actors, a governance model for the Marine Park, located in the municipality of Sesimbra （Portugal）. To pursue this goal, a PPGIS （public participation geographic information system） was developed, allowing the interaction, discussion and public participation of the stakeholders and actors involved. This PPGIS emerged as a crowdsourcing tool, with the purpose of assisting the georeferenced contributes from the local users of the Marine Park, regarding several relevant subjects, such as pollution, economic activities, opportunities and threats to the Marine Park, providing visual, analytical, and demonstrative qualities.
基金supported by the China United Gas Turbine Technology Co.Ltd.(Grant number J920)。
文摘Flame propagation speeds are reported for ammonia/hydrogen/air mixtures with equivalence ratios in the range of 0.5-1.5,preheated gas temperatures ranging from 298 K to 673 K and hydrogen volume fractions of0%,20%,and 50%.The measurements were conducted using a Bunsen burner and an optical schlieren system.The results show that the flame propagation speed and combustion stabilities of the premixed gases increase with increasing preheating temperature.The combustion stability is significantly improved under the 20%hydrogen volume fraction condition.For the NH_(3)/H_(2)mixtures with a hydrogen volume fraction of 50%,the flame propagation speed at 673 K with a stoichiometric ratio is approximately 4.85 times that at 298 K.The experimental results show that at 673 K,the flame propagation speed of the NH_(3)/H_(2)/air mixture increases by 7.8times when the hydrogen volume fraction increases from 20%to 80%.The numerical results predicted with the Mei,Shrestha,and Stagni mechanisms are compared with the experimental data.The mechanisms proposed by Shrestha and Stagni overestimate the flame propagation speed,especially at high preheating temperatures.The results predicted with the Mei mechanism are consistent with the available data.The concentrations of OH,H,O and NH_(2)are increased by the hydrogen addition;thus,the ammonia consumption is accelerated.
基金the National Natural Science Foundation of China(Grant No.11672126)Innovation Funded Project of Shanghai Aerospace Science and Technology(Grant No.SAST2015036)+4 种基金the Opening Grant from the Key Laboratory of Space Utilization,Chinese Academy of Sciences(LSU-2016-07-01)Funding of Jiangsu Innovation Program for Graduate Education(Grant No.KYZZ160170)the Fundamental Research Funds for the Central UniversitiesFunding for Outstanding Doctoral Dissertation in NUAA(Grant No.BCXJ16-10)The authors fully appreciate their financial supports.
文摘Scheduled for an Earth-to-Mars launch opportunity in 2020,the China’s Mars probe will arrive on Mars in 2021 with the primary objective of injecting an orbiter and placing a lander and a rover on the surface of the Red Planet.For China’s 2020 Mars exploration mission to achieve success,many key technologies must be realized.In this paper,China’s 2020 Mars mission and the spacecraft architecture are first introduced.Then,the preliminary launch opportunity,Earth–Mars transfer,Mars capture,and mission orbits are described.Finally,the main navigation schemes are summarized.
文摘This paper presents a novel power flow tracing (PFT) algorithm for electric networks with loopflow (ENL)—PFT(EN)L algorithm. During calculating process, the simplified network is obtained using the equivalent node for the loopflow part of a network. Graph theory is applied to determining the directed path from any generator-bus to load-buses with the proposed algorithm. Based on the AC load flow, the proportional sharing principle, series theory and the directed paths, the contribution of generators to the line flows and the extraction of loads from the generators can be calculated. The definitions and properties of auto-loopflow-coefficient (ALC) of an ENL are pro-posed. In this paper, two theorems have been proved: one is that the PFTL algorithm is always convergent with the properties of ALC; and the other is that the condition under which the whole contribution of any generator to all loads equals the output of the generator for a lossless ENL will be well satisfied with the PFTL algorithm. The developed algorithm has been tested on a number of test systems and the results show the feasibility and applicability of the approach.
基金supported in part by National Natural Science Foundation of China(U21B2015,61972300)in part by Young Scientists Fund of the National Natural Science Foundation of China(62202356)+1 种基金in part by Young Talent Fund of Association for Science and Technology in Shaanxi(20220113)in part by Intelligent Financial Software Engineering New Technology Joint Laboratory Project(99901220858)。
文摘Autoencoder-based rating prediction methods with external attributes have received wide attention due to their ability to accurately capture users'preferences.However,existing methods still have two significant limitations:i)External attributes are often unavailable in the real world due to privacy issues,leading to low quality of representations;and ii)existing methods lack considering complex associations in users'rating behaviors during the encoding process.To meet these challenges,this paper innovatively proposes an inherent-attribute-aware dual-graph autoencoder,named IADGAE,for rating prediction.To address the low quality of representations due to the unavailability of external attributes,we propose an inherent attribute perception module that mines inductive user active patterns and item popularity patterns from users'rating behaviors to strengthen user and item representations.To exploit the complex associations hidden in users’rating behaviors,we design an encoder on the item-item co-occurrence graph to capture the co-occurrence frequency features among items.Moreover,we propose a dual-graph feature encoder framework to simultaneously encode and fuse the high-order representations learned from the user-item rating graph and item-item co-occurrence graph.Extensive experiments on three real datasets demonstrate that IADGAE is effective and outperforms existing rating prediction methods,which achieves a significant improvement of 4.51%~41.63%in the RMSE metric.
文摘Lithium niobate （LiNbO3） is a useful photonic material for its electro-optic and nonlinear optical properties. In this paper, I will report developments of LiNbO3 based optical devices for fiber communication, including high-performance modulators and high efficiency wavelength converters.
文摘The optically based technique of electro-optic (EO) sampling has been used for diagnosing the internal high-speed signals of integrated circuits.One of the features that make the EO sampling technique very promising is a minimal probe: the EO sampling technique does not require an electrode and ground plane incorporated as part of a probe so that, compared with conventional metal probes, the invasiveness of an EO probe is minimal.
