This study explores the aerodynamic performance and flow field characteristics of supercritical carbon dioxide(sCO_(2))centrifugal compressors under varying operating conditions.In particular,the Sandia main compresso...This study explores the aerodynamic performance and flow field characteristics of supercritical carbon dioxide(sCO_(2))centrifugal compressors under varying operating conditions.In particular,the Sandia main compressor impeller model is used as a reference system.Through three-dimensional numerical simulations,we examine the Mach number distribution,temperature field,blade pressure pulsation spectra,and velocity field evolution,and identify accordingly the operating boundaries ensuring stability and the mechanisms responsible for performance degradation.Findings indicate a stable operating range for mass flow rate between 0.74 and 3.74 kg/s.At the lower limit(0.74 kg/s),the maximum Mach number within the compressor decreases by 28%,while the temperature gradient sharpens,entropy rises notably,and fluid density varies significantly.The maximum pressure near the blades increases by 6%,yet flow velocity near the blades and outlet declines,with a 19%reduction in peak speed.Consequently,isentropic efficiency falls by 13%.Conversely,at 3.74 kg/s,the maximum Mach number increases by 23.7%,with diminished temperature gradients and minor fluid density variations.However,insufficient enthalpy gain and intensified pressure pulsations near the blades result in a 12%pressure drop.Peak velocity within the impeller channel surges by 23%,amplifying velocity gradients,inducing flow separation,and ultimately reducing the pressure ratio from 1.47 to 1.34.展开更多
Osmanthus, an ornamental plants, is favored by people, and forecast of Osmanthus florescence is of vital significance for enjoying the sight. Based on 15 years of flowering observation data, analysis was made on agric...Osmanthus, an ornamental plants, is favored by people, and forecast of Osmanthus florescence is of vital significance for enjoying the sight. Based on 15 years of flowering observation data, analysis was made on agricultural meteorologi- cal conditions of Osmanthus in Guilin and the results showed that ground tempera- ture, humidity, precipitation, sunshine have significant effects on Osmanthus flores- cence. In forecasting florescence, therefore, it is necessary to take comprehensive consideration of weather conditions and changes in the future, to release Osman- thus flowering forecast as per method of combination of long-term forecasting and short-term forecast.展开更多
The effects of axisymmetric flow of a Powell-Eyring fluid over an impermeable radially stretching surface are presented. Characteristics of the heat transfer process are analyzed with a more realistic condition named ...The effects of axisymmetric flow of a Powell-Eyring fluid over an impermeable radially stretching surface are presented. Characteristics of the heat transfer process are analyzed with a more realistic condition named the convective boundary condition. Governing equations for the flow problem are derived by the boundary layer approximations. The modeled highly coupled partial differential system is converted into a system of ordinary differential equations with acceptable similarity transformations. The convergent series solutions for the resulting system are constructed and analyzed. Optimal values are obtained and presented in a numerical form using an optimal homotopy analysis method （OHAM）. The rheological characteristics of different parameters of the velocity and temperature profiles are presented graphically. Tabular variations of the skin friction coefficient and the Nusselt number are also calculated. It is observed that the temperature distribution shows opposite behavior for Prandtl and Biot numbers. Furthermore, the rate of heating/cooling is higher for both the Prandtl and Biot numbers.展开更多
The continuous belt machine in the high slope upward transportation prone to summarize the problems, carefully analyze the reasons and take the corresponding solution measures, is to ensure that the tunnel constructio...The continuous belt machine in the high slope upward transportation prone to summarize the problems, carefully analyze the reasons and take the corresponding solution measures, is to ensure that the tunnel construction can achieve high efficiency and high efficiency of the necessary conditions. As TBM is more and more applied to tunnel construction, the efficiency of tunnel construction have been greatly improved, and the supporting slag discharge mode has also become a hot topic in the engineering field. At present, the belt continuous conveying system has become an important equipment of tunnel slag transport system, and it has the characteristics of long transmission distance, continuous operation, convenient maintenance and high efficiency.展开更多
1 Introduction Currently,all six different continents have discovered potash deposits and potash-bearing salt lake saline water.However,the distribution is extremely uneven,which is mostly concentrated in Canada,Russi...1 Introduction Currently,all six different continents have discovered potash deposits and potash-bearing salt lake saline water.However,the distribution is extremely uneven,which is mostly concentrated in Canada,Russia,Middle-Asia and展开更多
In this work,we investigate two specific linear ADRC structures,namely output-and error-based.The former is considered a“standard”version of ADRC,a title obtained primarily thanks to its simplicity and effectiveness...In this work,we investigate two specific linear ADRC structures,namely output-and error-based.The former is considered a“standard”version of ADRC,a title obtained primarily thanks to its simplicity and effectiveness,which have spurred its adoption across multiple industries.The latter is found to be especially appealing to practitioners as its feedback error-driven structure bares similarities to conventional control solutions,like PI and PID.In this paper,we describe newly found connections between the two considered ADRC structures,which allowed us to formally establish conditions for their equivalence.Furthermore,the conducted comprehensive performance comparison between output-and error-based ADRCs has facilitated the identification of specific modules within them,which can now be conveniently used as building blocks,thus aiding the control designers in customizing ADRC-based solutions and making them most suitable for their applications.展开更多
As the world multipolarization and economic globalization are developing,competition in overall national strength is becoming increasingly fierce.Social development requires the students to possess English language ab...As the world multipolarization and economic globalization are developing,competition in overall national strength is becoming increasingly fierce.Social development requires the students to possess English language ability.More and more people propose that English education be implemented in the primary schools.However,by analyzing the practical situation of English education in China,to the author's opinion,it is infeasible to comprehensively implement English education in China's primary schools.展开更多
An integrated drainage information, analysis and management system （DIAMS） was developed and implemented for the New Jersey Department of Transportation （N/DOT）. The purpose of the DIAMS is to provide a useful too...An integrated drainage information, analysis and management system （DIAMS） was developed and implemented for the New Jersey Department of Transportation （N/DOT）. The purpose of the DIAMS is to provide a useful tool for managers to evaluate drainage infrastructure, to facilitate the determination of the present costs of preserving those in- frastructures, and to make decisions regarding the optimal use of their infrastructure budgets. The impetus for DIAMS is the culvert information management system （CIMS）, which is developed to manage the data for culvert pipes. DIAMS maintains and summa- rizes accumulated inspection data for all types of drainage infrastructure assets, including pipes, inlet/outlet structures, outfalls and manufactured treatment devices. DIAMS capa- bilities include identifying drainage infrastructure, maintaining inspection history, map- ping locations, predicting service life based on the current condition states, and assessing present asset value. It also includes unit cost values of 72 standard items to estimate the current cost for new assets with the ability to adjust for future inflation. In addition, DIAMS contains several different repair, rehabilitation and replacement options to remedy the drainage infrastructure. DIAMS can analyze asset information and determine decisions to inspect, rehabilitate, replace or do nothing at the project and network levels by comparing costs with risks and failures. Costs may be optimized to meet annual maintenance budget allocations by pfioritizing drainage infrastructure needing inspection, cleaning and repair. DIAMS functional modules include vendor data uploading, asset identification, system administration and financial analysis. Among the significant performance feature of DIAMS is its proactive nature, which affords decision makers the means of conducting a comprehensive financial analysis to determine the optimal proactive schedule for the proper maintenance actions and to prioritize them accordingly. Benefits of DIAMS include long-term savings that accrue by adopting optimized preventive maintenance strategies and facilitating compliance with Governmental Accounting Standards Board （GASB） and federal storm water regulations.展开更多
As rural B&Bs gain popularity amid growing demand for personalized tourism experiences,understanding the multifaceted drivers of customer decision-making is becoming critical.Existing research often examines indiv...As rural B&Bs gain popularity amid growing demand for personalized tourism experiences,understanding the multifaceted drivers of customer decision-making is becoming critical.Existing research often examines individual factors,leaving a gap in comprehending complex causal pathways.This study used online travelogue data,fuzzy-set qualitative comparative analysis(fsQCA)and necessary condition analysis(NCA)to examine the factors and combination pathways influencing customer behavioral intentions in rural B&Bs.The results indicate that customer behavioral intentions in rural B&Bs are influenced by multiple factors including the natural environment,material space,cultural space,quality of service,experience of home,entertainment education,culinary delights,surrounding environment,and value-added services.In addition,four main types of customer behavioral intentions in rural B&Bs were identified:Environmental immersion,Educative entertainment,Service experience,and Comprehensive perception.This study contributes to our understanding of customer behavioral intentions in rural tourism settings both practically,by offering actionable strategies for B&B operators,and theoretically,by enhancing the existing framework for studying them.展开更多
This paper uses automatic vehicle location （AVL） records to investigate the effect of weather conditions on the travel time reliability of on-road rail transit, through a case study of the Melbourne streetcar （tram...This paper uses automatic vehicle location （AVL） records to investigate the effect of weather conditions on the travel time reliability of on-road rail transit, through a case study of the Melbourne streetcar （tram） network. The datasets available were an extensive historica; AVL dataset as well as weather observations. The sample size used in the analysis included all trips made over a period of five years （2006-2010 inclusive）, during the morning peak （7 am-9 am） for fifteen randomly selected radial tram routes, all traveling to the Melbourne CBD create a linear model Ordinary least square （OLS） regression analysis was conducted to with tram travel time being the dependent variable. An alternative formulation of the model is also compared. Travel time was regressed on various weather effects including precipitation, air temperature, sea level pressure and wind speed; as well as indicator variables for weekends, public holidays and route numbers to investigate a correlation between weather condition and the on-time performance of the trams. The results indicate that only precipitation and air temperature are significant in their effect on tram travel time. The model demonstrates that on average, an additional millimeter of precipitation during the peak period adversely affects the average travel time during that period by approximately 8 s, that is, rainfall tends to increase the travel time. The effect of air temperature is less intuitive, with the model indicating that trams adhere more closely to schedule when the temperature is different in absolute terms to the mean operating conditions （taken as 15 ℃）.展开更多
Speed humps are the most common type of traffic calming devices due to their low cost and easy installation. However, in many Egyptian roads, considerable number of these humps is randomly placed without proper engine...Speed humps are the most common type of traffic calming devices due to their low cost and easy installation. However, in many Egyptian roads, considerable number of these humps is randomly placed without proper engineering studies and justifications. Deteri- oration of pavement condition is observed near these humps. This paper presents a case study applied to collect and analyze visual inspection data for the reason of evaluating the impact of speed humps on pavement condition on intercity rural roads. The paper used 52 speed humps located in an intercity two-lane, two-way road that connects two cities, Tahta and Gerga, in Upper Egypt. The total length of this road is about 34 km. Pavement condition index （PCI）, in road sections, near speed humps in the two directions of travel were calculated from the visual inspection measurements. The characteristics of each speed hump （width, height, and distance from preceding hump） were measured. Using statistical analyses, the correlations between the pavement conditions and hump char- acteristics were examined. Regression analysis models were developed to represent the relationships between pavement conditions and hump characteristics. Generally, the re- sults proved that the pavement conditions are greatly influenced by the presence of speed humps and hump characteristics.展开更多
基金National Science Foundation of China(grant numbers 52366009 and 52130607)Doble First-Class Key Programof Gansu Provincial Department of Education(grant number GCJ2022-38)+1 种基金2022 Gansu Provincial University Industry Support Plan Project(grant number 2022CYZC-21)KeyR&DProgramofGansu Province of China(grant number 22YF7GA163).
文摘This study explores the aerodynamic performance and flow field characteristics of supercritical carbon dioxide(sCO_(2))centrifugal compressors under varying operating conditions.In particular,the Sandia main compressor impeller model is used as a reference system.Through three-dimensional numerical simulations,we examine the Mach number distribution,temperature field,blade pressure pulsation spectra,and velocity field evolution,and identify accordingly the operating boundaries ensuring stability and the mechanisms responsible for performance degradation.Findings indicate a stable operating range for mass flow rate between 0.74 and 3.74 kg/s.At the lower limit(0.74 kg/s),the maximum Mach number within the compressor decreases by 28%,while the temperature gradient sharpens,entropy rises notably,and fluid density varies significantly.The maximum pressure near the blades increases by 6%,yet flow velocity near the blades and outlet declines,with a 19%reduction in peak speed.Consequently,isentropic efficiency falls by 13%.Conversely,at 3.74 kg/s,the maximum Mach number increases by 23.7%,with diminished temperature gradients and minor fluid density variations.However,insufficient enthalpy gain and intensified pressure pulsations near the blades result in a 12%pressure drop.Peak velocity within the impeller channel surges by 23%,amplifying velocity gradients,inducing flow separation,and ultimately reducing the pressure ratio from 1.47 to 1.34.
文摘Osmanthus, an ornamental plants, is favored by people, and forecast of Osmanthus florescence is of vital significance for enjoying the sight. Based on 15 years of flowering observation data, analysis was made on agricultural meteorologi- cal conditions of Osmanthus in Guilin and the results showed that ground tempera- ture, humidity, precipitation, sunshine have significant effects on Osmanthus flores- cence. In forecasting florescence, therefore, it is necessary to take comprehensive consideration of weather conditions and changes in the future, to release Osman- thus flowering forecast as per method of combination of long-term forecasting and short-term forecast.
文摘The effects of axisymmetric flow of a Powell-Eyring fluid over an impermeable radially stretching surface are presented. Characteristics of the heat transfer process are analyzed with a more realistic condition named the convective boundary condition. Governing equations for the flow problem are derived by the boundary layer approximations. The modeled highly coupled partial differential system is converted into a system of ordinary differential equations with acceptable similarity transformations. The convergent series solutions for the resulting system are constructed and analyzed. Optimal values are obtained and presented in a numerical form using an optimal homotopy analysis method （OHAM）. The rheological characteristics of different parameters of the velocity and temperature profiles are presented graphically. Tabular variations of the skin friction coefficient and the Nusselt number are also calculated. It is observed that the temperature distribution shows opposite behavior for Prandtl and Biot numbers. Furthermore, the rate of heating/cooling is higher for both the Prandtl and Biot numbers.
文摘The continuous belt machine in the high slope upward transportation prone to summarize the problems, carefully analyze the reasons and take the corresponding solution measures, is to ensure that the tunnel construction can achieve high efficiency and high efficiency of the necessary conditions. As TBM is more and more applied to tunnel construction, the efficiency of tunnel construction have been greatly improved, and the supporting slag discharge mode has also become a hot topic in the engineering field. At present, the belt continuous conveying system has become an important equipment of tunnel slag transport system, and it has the characteristics of long transmission distance, continuous operation, convenient maintenance and high efficiency.
基金funded by National Program on Key Basic Research Project of China - 973 Program" Potash formation mechanism, conditions and late evolution in Ordovician ancient epicontinental sea basin, Erdos" (No. 2011CB403001)China Geological survey work Program - " Potash resources investigation and evaluation in Northern Shaanxi Ordovician Salt Basin " (No. 1212011085516)
文摘1 Introduction Currently,all six different continents have discovered potash deposits and potash-bearing salt lake saline water.However,the distribution is extremely uneven,which is mostly concentrated in Canada,Russia,Middle-Asia and
基金The work of Dr.R.Madonski was supported by the Fundamental Research Funds for the Central Universities(Project No.21620335)The work of Dr.M.Stankovic was supported by the International Foreign Expert Project Fund of Jinan University(Project No.G2021199027L,coordinator:Dr.Hui Deng).
文摘In this work,we investigate two specific linear ADRC structures,namely output-and error-based.The former is considered a“standard”version of ADRC,a title obtained primarily thanks to its simplicity and effectiveness,which have spurred its adoption across multiple industries.The latter is found to be especially appealing to practitioners as its feedback error-driven structure bares similarities to conventional control solutions,like PI and PID.In this paper,we describe newly found connections between the two considered ADRC structures,which allowed us to formally establish conditions for their equivalence.Furthermore,the conducted comprehensive performance comparison between output-and error-based ADRCs has facilitated the identification of specific modules within them,which can now be conveniently used as building blocks,thus aiding the control designers in customizing ADRC-based solutions and making them most suitable for their applications.
文摘As the world multipolarization and economic globalization are developing,competition in overall national strength is becoming increasingly fierce.Social development requires the students to possess English language ability.More and more people propose that English education be implemented in the primary schools.However,by analyzing the practical situation of English education in China,to the author's opinion,it is infeasible to comprehensively implement English education in China's primary schools.
基金sponsored by a research contract from the NJDOT(FHWA-NJ-2012-010)
文摘An integrated drainage information, analysis and management system （DIAMS） was developed and implemented for the New Jersey Department of Transportation （N/DOT）. The purpose of the DIAMS is to provide a useful tool for managers to evaluate drainage infrastructure, to facilitate the determination of the present costs of preserving those in- frastructures, and to make decisions regarding the optimal use of their infrastructure budgets. The impetus for DIAMS is the culvert information management system （CIMS）, which is developed to manage the data for culvert pipes. DIAMS maintains and summa- rizes accumulated inspection data for all types of drainage infrastructure assets, including pipes, inlet/outlet structures, outfalls and manufactured treatment devices. DIAMS capa- bilities include identifying drainage infrastructure, maintaining inspection history, map- ping locations, predicting service life based on the current condition states, and assessing present asset value. It also includes unit cost values of 72 standard items to estimate the current cost for new assets with the ability to adjust for future inflation. In addition, DIAMS contains several different repair, rehabilitation and replacement options to remedy the drainage infrastructure. DIAMS can analyze asset information and determine decisions to inspect, rehabilitate, replace or do nothing at the project and network levels by comparing costs with risks and failures. Costs may be optimized to meet annual maintenance budget allocations by pfioritizing drainage infrastructure needing inspection, cleaning and repair. DIAMS functional modules include vendor data uploading, asset identification, system administration and financial analysis. Among the significant performance feature of DIAMS is its proactive nature, which affords decision makers the means of conducting a comprehensive financial analysis to determine the optimal proactive schedule for the proper maintenance actions and to prioritize them accordingly. Benefits of DIAMS include long-term savings that accrue by adopting optimized preventive maintenance strategies and facilitating compliance with Governmental Accounting Standards Board （GASB） and federal storm water regulations.
基金The Major Project of the National Social Science Fund of Art of China(21ZD07)。
文摘As rural B&Bs gain popularity amid growing demand for personalized tourism experiences,understanding the multifaceted drivers of customer decision-making is becoming critical.Existing research often examines individual factors,leaving a gap in comprehending complex causal pathways.This study used online travelogue data,fuzzy-set qualitative comparative analysis(fsQCA)and necessary condition analysis(NCA)to examine the factors and combination pathways influencing customer behavioral intentions in rural B&Bs.The results indicate that customer behavioral intentions in rural B&Bs are influenced by multiple factors including the natural environment,material space,cultural space,quality of service,experience of home,entertainment education,culinary delights,surrounding environment,and value-added services.In addition,four main types of customer behavioral intentions in rural B&Bs were identified:Environmental immersion,Educative entertainment,Service experience,and Comprehensive perception.This study contributes to our understanding of customer behavioral intentions in rural tourism settings both practically,by offering actionable strategies for B&B operators,and theoretically,by enhancing the existing framework for studying them.
基金supported by the Australian Research Council(No.DE130100205)
文摘This paper uses automatic vehicle location （AVL） records to investigate the effect of weather conditions on the travel time reliability of on-road rail transit, through a case study of the Melbourne streetcar （tram） network. The datasets available were an extensive historica; AVL dataset as well as weather observations. The sample size used in the analysis included all trips made over a period of five years （2006-2010 inclusive）, during the morning peak （7 am-9 am） for fifteen randomly selected radial tram routes, all traveling to the Melbourne CBD create a linear model Ordinary least square （OLS） regression analysis was conducted to with tram travel time being the dependent variable. An alternative formulation of the model is also compared. Travel time was regressed on various weather effects including precipitation, air temperature, sea level pressure and wind speed; as well as indicator variables for weekends, public holidays and route numbers to investigate a correlation between weather condition and the on-time performance of the trams. The results indicate that only precipitation and air temperature are significant in their effect on tram travel time. The model demonstrates that on average, an additional millimeter of precipitation during the peak period adversely affects the average travel time during that period by approximately 8 s, that is, rainfall tends to increase the travel time. The effect of air temperature is less intuitive, with the model indicating that trams adhere more closely to schedule when the temperature is different in absolute terms to the mean operating conditions （taken as 15 ℃）.
文摘Speed humps are the most common type of traffic calming devices due to their low cost and easy installation. However, in many Egyptian roads, considerable number of these humps is randomly placed without proper engineering studies and justifications. Deteri- oration of pavement condition is observed near these humps. This paper presents a case study applied to collect and analyze visual inspection data for the reason of evaluating the impact of speed humps on pavement condition on intercity rural roads. The paper used 52 speed humps located in an intercity two-lane, two-way road that connects two cities, Tahta and Gerga, in Upper Egypt. The total length of this road is about 34 km. Pavement condition index （PCI）, in road sections, near speed humps in the two directions of travel were calculated from the visual inspection measurements. The characteristics of each speed hump （width, height, and distance from preceding hump） were measured. Using statistical analyses, the correlations between the pavement conditions and hump char- acteristics were examined. Regression analysis models were developed to represent the relationships between pavement conditions and hump characteristics. Generally, the re- sults proved that the pavement conditions are greatly influenced by the presence of speed humps and hump characteristics.
