Shape memory alloys （SMAs） are the developing advanced materials due to their versatile specific properties such as pseudoelasticity, shape memory effect （SME）, biocompatibility, high specific strength, high corro...Shape memory alloys （SMAs） are the developing advanced materials due to their versatile specific properties such as pseudoelasticity, shape memory effect （SME）, biocompatibility, high specific strength, high corrosion resistance, high wear resistance and high anti-fatigue property. Therefore, the SMAs are used in many applications such as aerospace, medical and automobile. However, the conventional machining of SMAs causes serious tool wear, time consuming and less dimensional deformity due to severe strain hardening and pseudoelasticity. These materials can be machined using non-conventional methods such as laser machining, water jet machining （WJM） and electrochemical machining （ECM）, but these processes are limited to complexity and mechanical properties of the component. Electrical discharge machining （EDM） and wire EDM （WEDM） show high capability to machine SMAs of complex shapes with precise dimensions. The aim of this work is to present the consolidated references on the machining of SMAs using EDM and WEDM and subsequently identify the research gaps. In support to these research gaps, this work has also evolved the future research directions.展开更多
This paper reports the application of pulse discharges along with catalysts in treat- ing the exhaust gas at higher temperatures. In the present work a plasma reactor, filled with catalysts, called as plasma catalytic...This paper reports the application of pulse discharges along with catalysts in treat- ing the exhaust gas at higher temperatures. In the present work a plasma reactor, filled with catalysts, called as plasma catalytic reactor, is studied for removal of oxides of nitrogen, total hydrocarbons and carbon monoxide. The experiments are conducted on an actual diesel engine exhaust at no-load and at different temperatures starting from room temperature to 300°C. The removal efficiencies of these pollutants are studied. The experiments are carried out with both con- ventional and non-conventional catalysts. The idea is to explore the pollutant removal efficiency characteristics by non-conventional catalysts. The efficiency results are compared with that of conventional catalysts. The experiments are carried out at a constant pulse repetition rate of 120 pps. Both pellet and honeycomb type catalysts are used in the study.展开更多
l-Methyl-3-ethyl imidazolium bromide[meim]Br/basic alumina（Al2O3） has been found to promote the cyclocondensation of chloroacetone/chloroethyl acetate with salicylaldehydes under conventional as well as microwave ir...l-Methyl-3-ethyl imidazolium bromide[meim]Br/basic alumina（Al2O3） has been found to promote the cyclocondensation of chloroacetone/chloroethyl acetate with salicylaldehydes under conventional as well as microwave irradiation to yield benzofuran derivatives.展开更多
In present study concentration of some metals (Magnesium, Nickel and Calcium) were determined in soil and different parts of Avena sativa treated with poultry waste grown in the pots. Nine different treatments of poul...In present study concentration of some metals (Magnesium, Nickel and Calcium) were determined in soil and different parts of Avena sativa treated with poultry waste grown in the pots. Nine different treatments of poultry waste were used: 0 (control), 60, 90, 120 and 150 kg/ha applied to soil as full doses before sowing, and 60, 90, 120, and 150 applied as two equal splits, 1st before sowing and the 2nd before flower instigation. The samples of soil were obtained after mixing the poultry waste with soil in each pot before sowing. Different parts (roots, leaves, and seeds) of plants were taken after 90 days of sowing and after grain filling. Samples of soil and forages were analyzed. Mg concentrations found both in soil and plants were non-significantly affected by treatments and were lower than the requirements of ruminants in forage crops, but above requirement of forages in soil. Soil and forage Ni was affected non-significantly from the treatments of poultry waste and soil and forage Ni levels were found to be lower than the toxic level for animals and forages. Soil Ca was affected non-significantly by treatments having far lower values than the requirements of both forage species and ruminants. The study showed that soil Mg was higher and Ca was lower than the requirements of forages, but forage Mg and Ca were not fulfilling the requirements of livestock indicating the non significant effect of poultry waste on their concentrations. From the results of this study it has been anticipated that various deficiency problems in livestock may be resulted as these elements play very important role in animals’ metabolic progression. Therefore, soil amendment with poultry manure along with other synthetic fertilizers for enhancing the levels of various minerals is acceptable. The soil amendment and specifically tailored mineral mixture with appropriate proportion of these elements is the dire needs for livestock consuming Avena sativa in pasture treated with poultry waste.展开更多
In indoor design innovation, the material role can not be ignored. In indoor design, using non-conventional decoration materials can make space more personalized and charming. This is one of the material innovation mo...In indoor design innovation, the material role can not be ignored. In indoor design, using non-conventional decoration materials can make space more personalized and charming. This is one of the material innovation modes and also one of the indoor design innovation modes. The design method should obtain more attention.展开更多
A cross-sectional survey was conducted to establish the utilisation of non-conventional animal waste in multiple livestock species systems. Farmers (150) were selected from four out of ten districts of Central Uganda ...A cross-sectional survey was conducted to establish the utilisation of non-conventional animal waste in multiple livestock species systems. Farmers (150) were selected from four out of ten districts of Central Uganda in Lake Victoria Crescent. A structured questionnaire was used and descriptive analysis showed that over 80% are smallholder farmers on 3.0) years. Household husbands (80%) significantly (P 1.0) as they cause poor livestock health due to pathogens, parasites and toxins which are associated (OD > 1.0) with poor growth, mortality and condemnation of livestock products. The remedy to unsafe non-conventional feeds is to apply effective solar-heating (75%), chemical and ensiling treatment methods. The study showed that there are no significant (P < 0.001) public health risks associated with utilising treated non-conventional feeds instead it improves production and sustainability of multiple livestock species systems.展开更多
Augmented reality(AR)is an emerging dynamic technology that effectively supports education across different levels.The increased use of mobile devices has an even greater impact.As the demand for AR applications in ed...Augmented reality(AR)is an emerging dynamic technology that effectively supports education across different levels.The increased use of mobile devices has an even greater impact.As the demand for AR applications in education continues to increase,educators actively seek innovative and immersive methods to engage students in learning.However,exploring these possibilities also entails identifying and overcoming existing barriers to optimal educational integration.Concurrently,this surge in demand has prompted the identification of specific barriers,one of which is three-dimensional(3D)modeling.Creating 3D objects for augmented reality education applications can be challenging and time-consuming for the educators.To address this,we have developed a pipeline that creates realistic 3D objects from the two-dimensional(2D)photograph.Applications for augmented and virtual reality can then utilize these created 3D objects.We evaluated the proposed pipeline based on the usability of the 3D object and performance metrics.Quantitatively,with 117 respondents,the co-creation team was surveyed with openended questions to evaluate the precision of the 3D object created by the proposed photogrammetry pipeline.We analyzed the survey data using descriptive-analytical methods and found that the proposed pipeline produces 3D models that are positively accurate when compared to real-world objects,with an average mean score above 8.This study adds new knowledge in creating 3D objects for augmented reality applications by using the photogrammetry technique;finally,it discusses potential problems and future research directions for 3D objects in the education sector.展开更多
In order to improve the accuracy of the photogrammetric joint roughness coefficient(JRC)value,the present study proposed a novel method combining an autonomous shooting parameter selection algorithm with a composite e...In order to improve the accuracy of the photogrammetric joint roughness coefficient(JRC)value,the present study proposed a novel method combining an autonomous shooting parameter selection algorithm with a composite error model.Firstly,according to the depth map-based photogrammetric theory,the estimation of JRC from a three-dimensional(3D)digital surface model of rock discontinuities was presented.Secondly,an automatic shooting parameter selection algorithm was novelly proposed to establish the 3D model dataset of rock discontinuities with varying shooting parameters and target sizes.Meanwhile,the photogrammetric tests were performed with custom-built equipment capable of adjusting baseline lengths,and a total of 36 sets of JRC data was gathered via a combination of laboratory and field tests.Then,by combining the theory of point cloud coordinate computation error with the equation of JRC calculation,a composite error model controlled by the shooting parameters was proposed.This newly proposed model was validated via the 3D model dataset,demonstrating the capability to correct initially obtained JRC values solely based on shooting parameters.Furthermore,the implementation of this correction can significantly reduce errors in JRC values obtained via photographic measurement.Subsequently,our proposed error model was integrated into the shooting parameter selection algorithm,thus improving the rationality and convenience of selecting suitable shooting parameter combinations when dealing with target rock masses with different sizes.Moreover,the optimal combination of three shooting parameters was offered.JRC values resulting from various combinations of shooting parameters were verified by comparing them with 3D laser scan data.Finally,the application scope and limitations of the newly proposed approach were further addressed.展开更多
Potholes are the most prevalent type of structural defect found on roads,caused by aging infrastructure,heavy rains,heavy traffic,thin or weak substructures,and other factors.Regular assessment of road conditions is e...Potholes are the most prevalent type of structural defect found on roads,caused by aging infrastructure,heavy rains,heavy traffic,thin or weak substructures,and other factors.Regular assessment of road conditions is essential for maintaining and improving road networks.Current techniques for identifying potholes on urban roadways primarily rely on public reporting,such as hotlines or social networking websites,which are both timeconsuming and inefficient.This study aims to detect potholes using Unmanned Aerial Vehicles(UAVs)images,enabling accurate analysis of their size,shape,and location,thereby enhancing detection efficiency compared to conventional methods.It compared area and volume measurements of potholes derived from UAV models with those obtained through traditional methods,revealing discrepancies and highlighting UAVs’potential for providing more accurate data with appropriate settings.The study found measurement errors ranging from 90 to 8200 cm^(2) in area and 2000 to 31,000 cm^(3) in volume,emphasizing the need for careful data handling in assessments.This study demonstrates UAV technology’s effectiveness in pothole detection,providing insights that support the adoption of aerial photogrammetry for road maintenance.This approach has the potential to improve efficiency in infrastructure management.By appropriately adjusting altitude settings and parameters based on pothole size and depth,UAVs can detect potholes effectively.To achieve more accurate results,the study recommends analyzing a larger number of potholes rather than limiting the focus to a single pothole.展开更多
0 INTRODUCTION Rock masses are inherently discontinuous,with fractures and joints governing their mechanical behavior and stability(Liu et al.,2024;Shang et al.,2018;Lisjak and Grasselli,2014;Scholtès and Donz...0 INTRODUCTION Rock masses are inherently discontinuous,with fractures and joints governing their mechanical behavior and stability(Liu et al.,2024;Shang et al.,2018;Lisjak and Grasselli,2014;Scholtès and Donzé,2012;Jiang et al.,2009;Pine et al.,2006;Aydan et al.,1989).展开更多
Stem volume estimation is crucial in forest ecology and management,particularly for timber harvesting strategies and carbon stock assessments.This study aimed to develop a variable-exponent taper equation specifically...Stem volume estimation is crucial in forest ecology and management,particularly for timber harvesting strategies and carbon stock assessments.This study aimed to develop a variable-exponent taper equation specifically tailored to savanna tree species using close-range photogrammetry(CRP)data and to evaluate its performance against conventional volume equations for stem volume estimation.A dataset of 30 trees across five dominant savanna species was used to fit the taper model,which was validated using a separate dataset of 322 trees from 14 species.The results demonstrated significant improvements in volume estimation accuracy when using the taper equation.At the tree level,the root mean square error(RMSE)decreased by 47%,from 598 to 319 dm^(3),and the mean absolute bias(MAB)by 48%,from 328 to 172 dm3,compared to volume equations.Similarly,at the plot level,RMSE was reduced by 42% and MAB by 40%.The model performed well for species with regular forms.However,species with irregular tapers exhibited higher errors,reflecting the challenges of modeling stem forms of mixed species.The use of CRP proved valuable,providing high-resolution diameter measurements that improved model parameterization.This study underscores the importance of advanced data collection methods for enhancing taper model accuracy and suggests that further species-specific adjustments are needed to improve performance for species with irregular forms.The findings support the broader application of taper equations for improving stem volume estimates in savanna ecosystems,contributing to better forest management and resource monitoring practices.展开更多
This study provides the first systematic evaluation of image resolution’s effect (50-300 PPI, pixels per inch) on UAV (unmanned aerial vehicle)-based digital close-range photogrammetry accuracy in civil engineering a...This study provides the first systematic evaluation of image resolution’s effect (50-300 PPI, pixels per inch) on UAV (unmanned aerial vehicle)-based digital close-range photogrammetry accuracy in civil engineering applications, such as infrastructure monitoring and heritage preservation. Using a high-resolution UAV with a 20 MP (MegaPixels) sensor, four images of a brick wall test field were captured and processed in Agisoft Metashape, with resolutions compared against Leica T2002 theodolite measurements (1.0 mm accuracy). Advanced statistical methods (ANOVA (analysis of variance), Tukey tests, Monte Carlo simulations) and ground control points validated the results. Accuracy improved from 25 mm at 50 PPI to 5 mm at 150 PPI (p < 0.01), plateauing at 4 mm beyond 200 PPI, while 150 PPI reduced processing time by 62% compared to 300 PPI. Unlike prior studies, this research uniquely isolates resolution effects in a controlled civil engineering context, offering a novel 150 PPI threshold that balances precision and efficiency. This threshold supports Saudi Vision 2030’s smart infrastructure goals for megaprojects like NEOM, providing a scalable framework for global applications. Future research should leverage deep learning to optimize resolutions in dynamic environments.展开更多
The estimation of orientation parameters and correction of lens distortion are crucial problems in the field of Unmanned Aerial Vehicles(UAVs)photogrammetry.In recent years,the utilization of UAVs for aerial photogram...The estimation of orientation parameters and correction of lens distortion are crucial problems in the field of Unmanned Aerial Vehicles(UAVs)photogrammetry.In recent years,the utilization of UAVs for aerial photogrammetry has witnessed a surge in popularity.Typically,UAVs are equipped with low-cost non-metric cameras and a Position and Orientation System(POS).Unfortunately,the Interior Orientation Parameters(IOPs)of the non-metric cameras are not fixed.Whether the lens distortions are large or small,they effect the image coordinates accordingly.Additionally,Inertial Measurement Units(IMUs)often have observation errors.To address these challenges and improve parameter estimation for UAVs Light Detection and Ranging(LiDAR)and photogrammetry,this paper analyzes the accuracy of POS observations obtained from Global Navigation Satellite System Real Time Kinematic(GNSS-RTK)and IMU data.A method that incorporates additional known conditions for parameter estimation,a series of algorithms to simultaneously solve for IOPs,Exterior Orientation Parameters(EOPs),and camera lens distortion correction parameters are proposed.Extensive experiments demonstrate that the coordinates measured by GNSS-RTK can be directly used as linear EOPs;however,angular EOP measurements from IMUs exhibit relatively large errors compared to adjustment results and require correction during the adjustment process.The IOPs of non-metric cameras vary slightly between images but need to be treated as unknown parameters in high precision applications.Furthermore,it is found that the Ebner systematic error model is sensitive to the choice of the magnification parameter of the photographic baseline length in images,it should be set as less than or equal to one third of the photographic baseline to ensure stable solutions.展开更多
多相机三维数字图像相关(three-dimensional digital image correlation,3D-DIC)系统在测量核燃料包壳管应变的实际应用中,多相机标定环节存在坐标系转换引发的累计误差增加及全局优化能力不足等问题。为此,提出一种基于空间标定靶的多...多相机三维数字图像相关(three-dimensional digital image correlation,3D-DIC)系统在测量核燃料包壳管应变的实际应用中,多相机标定环节存在坐标系转换引发的累计误差增加及全局优化能力不足等问题。为此,提出一种基于空间标定靶的多相机全局标定方法。首先,提出为各相机在标定靶每个位姿下提供外方位参数初值的方法,保证空间后方交会正确收敛;其次,提出多相机多位姿光束平差(bundle adjustment,BA)方法,保证多相机标定精度达到全局最优。实验结果表明,该方法的标定精度较直接线性变换(direct linear transformation,DLT)方法提高了55.1%,最大位移误差标准差降低了16.3%。同时,该方法无需对标志点进行手动编号,使标定过程实现了自动化,标定效率更高。展开更多
文摘Shape memory alloys （SMAs） are the developing advanced materials due to their versatile specific properties such as pseudoelasticity, shape memory effect （SME）, biocompatibility, high specific strength, high corrosion resistance, high wear resistance and high anti-fatigue property. Therefore, the SMAs are used in many applications such as aerospace, medical and automobile. However, the conventional machining of SMAs causes serious tool wear, time consuming and less dimensional deformity due to severe strain hardening and pseudoelasticity. These materials can be machined using non-conventional methods such as laser machining, water jet machining （WJM） and electrochemical machining （ECM）, but these processes are limited to complexity and mechanical properties of the component. Electrical discharge machining （EDM） and wire EDM （WEDM） show high capability to machine SMAs of complex shapes with precise dimensions. The aim of this work is to present the consolidated references on the machining of SMAs using EDM and WEDM and subsequently identify the research gaps. In support to these research gaps, this work has also evolved the future research directions.
文摘This paper reports the application of pulse discharges along with catalysts in treat- ing the exhaust gas at higher temperatures. In the present work a plasma reactor, filled with catalysts, called as plasma catalytic reactor, is studied for removal of oxides of nitrogen, total hydrocarbons and carbon monoxide. The experiments are conducted on an actual diesel engine exhaust at no-load and at different temperatures starting from room temperature to 300°C. The removal efficiencies of these pollutants are studied. The experiments are carried out with both con- ventional and non-conventional catalysts. The idea is to explore the pollutant removal efficiency characteristics by non-conventional catalysts. The efficiency results are compared with that of conventional catalysts. The experiments are carried out at a constant pulse repetition rate of 120 pps. Both pellet and honeycomb type catalysts are used in the study.
文摘l-Methyl-3-ethyl imidazolium bromide[meim]Br/basic alumina（Al2O3） has been found to promote the cyclocondensation of chloroacetone/chloroethyl acetate with salicylaldehydes under conventional as well as microwave irradiation to yield benzofuran derivatives.
文摘In present study concentration of some metals (Magnesium, Nickel and Calcium) were determined in soil and different parts of Avena sativa treated with poultry waste grown in the pots. Nine different treatments of poultry waste were used: 0 (control), 60, 90, 120 and 150 kg/ha applied to soil as full doses before sowing, and 60, 90, 120, and 150 applied as two equal splits, 1st before sowing and the 2nd before flower instigation. The samples of soil were obtained after mixing the poultry waste with soil in each pot before sowing. Different parts (roots, leaves, and seeds) of plants were taken after 90 days of sowing and after grain filling. Samples of soil and forages were analyzed. Mg concentrations found both in soil and plants were non-significantly affected by treatments and were lower than the requirements of ruminants in forage crops, but above requirement of forages in soil. Soil and forage Ni was affected non-significantly from the treatments of poultry waste and soil and forage Ni levels were found to be lower than the toxic level for animals and forages. Soil Ca was affected non-significantly by treatments having far lower values than the requirements of both forage species and ruminants. The study showed that soil Mg was higher and Ca was lower than the requirements of forages, but forage Mg and Ca were not fulfilling the requirements of livestock indicating the non significant effect of poultry waste on their concentrations. From the results of this study it has been anticipated that various deficiency problems in livestock may be resulted as these elements play very important role in animals’ metabolic progression. Therefore, soil amendment with poultry manure along with other synthetic fertilizers for enhancing the levels of various minerals is acceptable. The soil amendment and specifically tailored mineral mixture with appropriate proportion of these elements is the dire needs for livestock consuming Avena sativa in pasture treated with poultry waste.
文摘In indoor design innovation, the material role can not be ignored. In indoor design, using non-conventional decoration materials can make space more personalized and charming. This is one of the material innovation modes and also one of the indoor design innovation modes. The design method should obtain more attention.
文摘A cross-sectional survey was conducted to establish the utilisation of non-conventional animal waste in multiple livestock species systems. Farmers (150) were selected from four out of ten districts of Central Uganda in Lake Victoria Crescent. A structured questionnaire was used and descriptive analysis showed that over 80% are smallholder farmers on 3.0) years. Household husbands (80%) significantly (P 1.0) as they cause poor livestock health due to pathogens, parasites and toxins which are associated (OD > 1.0) with poor growth, mortality and condemnation of livestock products. The remedy to unsafe non-conventional feeds is to apply effective solar-heating (75%), chemical and ensiling treatment methods. The study showed that there are no significant (P < 0.001) public health risks associated with utilising treated non-conventional feeds instead it improves production and sustainability of multiple livestock species systems.
文摘Augmented reality(AR)is an emerging dynamic technology that effectively supports education across different levels.The increased use of mobile devices has an even greater impact.As the demand for AR applications in education continues to increase,educators actively seek innovative and immersive methods to engage students in learning.However,exploring these possibilities also entails identifying and overcoming existing barriers to optimal educational integration.Concurrently,this surge in demand has prompted the identification of specific barriers,one of which is three-dimensional(3D)modeling.Creating 3D objects for augmented reality education applications can be challenging and time-consuming for the educators.To address this,we have developed a pipeline that creates realistic 3D objects from the two-dimensional(2D)photograph.Applications for augmented and virtual reality can then utilize these created 3D objects.We evaluated the proposed pipeline based on the usability of the 3D object and performance metrics.Quantitatively,with 117 respondents,the co-creation team was surveyed with openended questions to evaluate the precision of the 3D object created by the proposed photogrammetry pipeline.We analyzed the survey data using descriptive-analytical methods and found that the proposed pipeline produces 3D models that are positively accurate when compared to real-world objects,with an average mean score above 8.This study adds new knowledge in creating 3D objects for augmented reality applications by using the photogrammetry technique;finally,it discusses potential problems and future research directions for 3D objects in the education sector.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52225904 and 52039007)the Fundamental Research Funds for the Central Universities,CHD(Grant No.300102212207).
文摘In order to improve the accuracy of the photogrammetric joint roughness coefficient(JRC)value,the present study proposed a novel method combining an autonomous shooting parameter selection algorithm with a composite error model.Firstly,according to the depth map-based photogrammetric theory,the estimation of JRC from a three-dimensional(3D)digital surface model of rock discontinuities was presented.Secondly,an automatic shooting parameter selection algorithm was novelly proposed to establish the 3D model dataset of rock discontinuities with varying shooting parameters and target sizes.Meanwhile,the photogrammetric tests were performed with custom-built equipment capable of adjusting baseline lengths,and a total of 36 sets of JRC data was gathered via a combination of laboratory and field tests.Then,by combining the theory of point cloud coordinate computation error with the equation of JRC calculation,a composite error model controlled by the shooting parameters was proposed.This newly proposed model was validated via the 3D model dataset,demonstrating the capability to correct initially obtained JRC values solely based on shooting parameters.Furthermore,the implementation of this correction can significantly reduce errors in JRC values obtained via photographic measurement.Subsequently,our proposed error model was integrated into the shooting parameter selection algorithm,thus improving the rationality and convenience of selecting suitable shooting parameter combinations when dealing with target rock masses with different sizes.Moreover,the optimal combination of three shooting parameters was offered.JRC values resulting from various combinations of shooting parameters were verified by comparing them with 3D laser scan data.Finally,the application scope and limitations of the newly proposed approach were further addressed.
基金Ministry of Higher Education(MOHE)are greatly acknowledged for providing the Fundamental Research Grant Scheme(Grant No.FRGS/1/2021/WAB07/UITM/02/2)GPK fund(Grant No.600-RMC/GPK 5/3(223/2020))College of Built Environment,Universiti Teknologi MARA(UiTM)and Research Management Centre(RMC)to enable this research to be carried out.
文摘Potholes are the most prevalent type of structural defect found on roads,caused by aging infrastructure,heavy rains,heavy traffic,thin or weak substructures,and other factors.Regular assessment of road conditions is essential for maintaining and improving road networks.Current techniques for identifying potholes on urban roadways primarily rely on public reporting,such as hotlines or social networking websites,which are both timeconsuming and inefficient.This study aims to detect potholes using Unmanned Aerial Vehicles(UAVs)images,enabling accurate analysis of their size,shape,and location,thereby enhancing detection efficiency compared to conventional methods.It compared area and volume measurements of potholes derived from UAV models with those obtained through traditional methods,revealing discrepancies and highlighting UAVs’potential for providing more accurate data with appropriate settings.The study found measurement errors ranging from 90 to 8200 cm^(2) in area and 2000 to 31,000 cm^(3) in volume,emphasizing the need for careful data handling in assessments.This study demonstrates UAV technology’s effectiveness in pothole detection,providing insights that support the adoption of aerial photogrammetry for road maintenance.This approach has the potential to improve efficiency in infrastructure management.By appropriately adjusting altitude settings and parameters based on pothole size and depth,UAVs can detect potholes effectively.To achieve more accurate results,the study recommends analyzing a larger number of potholes rather than limiting the focus to a single pothole.
基金supported by the National Key R&D Program of China(No.2022YFC3080200)。
文摘0 INTRODUCTION Rock masses are inherently discontinuous,with fractures and joints governing their mechanical behavior and stability(Liu et al.,2024;Shang et al.,2018;Lisjak and Grasselli,2014;Scholtès and Donzé,2012;Jiang et al.,2009;Pine et al.,2006;Aydan et al.,1989).
基金partially funded by the International Foundation for Science(Grant No:I-1-D-6066-1).
文摘Stem volume estimation is crucial in forest ecology and management,particularly for timber harvesting strategies and carbon stock assessments.This study aimed to develop a variable-exponent taper equation specifically tailored to savanna tree species using close-range photogrammetry(CRP)data and to evaluate its performance against conventional volume equations for stem volume estimation.A dataset of 30 trees across five dominant savanna species was used to fit the taper model,which was validated using a separate dataset of 322 trees from 14 species.The results demonstrated significant improvements in volume estimation accuracy when using the taper equation.At the tree level,the root mean square error(RMSE)decreased by 47%,from 598 to 319 dm^(3),and the mean absolute bias(MAB)by 48%,from 328 to 172 dm3,compared to volume equations.Similarly,at the plot level,RMSE was reduced by 42% and MAB by 40%.The model performed well for species with regular forms.However,species with irregular tapers exhibited higher errors,reflecting the challenges of modeling stem forms of mixed species.The use of CRP proved valuable,providing high-resolution diameter measurements that improved model parameterization.This study underscores the importance of advanced data collection methods for enhancing taper model accuracy and suggests that further species-specific adjustments are needed to improve performance for species with irregular forms.The findings support the broader application of taper equations for improving stem volume estimates in savanna ecosystems,contributing to better forest management and resource monitoring practices.
文摘This study provides the first systematic evaluation of image resolution’s effect (50-300 PPI, pixels per inch) on UAV (unmanned aerial vehicle)-based digital close-range photogrammetry accuracy in civil engineering applications, such as infrastructure monitoring and heritage preservation. Using a high-resolution UAV with a 20 MP (MegaPixels) sensor, four images of a brick wall test field were captured and processed in Agisoft Metashape, with resolutions compared against Leica T2002 theodolite measurements (1.0 mm accuracy). Advanced statistical methods (ANOVA (analysis of variance), Tukey tests, Monte Carlo simulations) and ground control points validated the results. Accuracy improved from 25 mm at 50 PPI to 5 mm at 150 PPI (p < 0.01), plateauing at 4 mm beyond 200 PPI, while 150 PPI reduced processing time by 62% compared to 300 PPI. Unlike prior studies, this research uniquely isolates resolution effects in a controlled civil engineering context, offering a novel 150 PPI threshold that balances precision and efficiency. This threshold supports Saudi Vision 2030’s smart infrastructure goals for megaprojects like NEOM, providing a scalable framework for global applications. Future research should leverage deep learning to optimize resolutions in dynamic environments.
基金Natural Science Foundation of Hunan Province,China(No.2024JJ8335)Open Topic of Hunan Geospatial Information Engineering and Technology Research Center,China(No.HNGIET2023004).
文摘The estimation of orientation parameters and correction of lens distortion are crucial problems in the field of Unmanned Aerial Vehicles(UAVs)photogrammetry.In recent years,the utilization of UAVs for aerial photogrammetry has witnessed a surge in popularity.Typically,UAVs are equipped with low-cost non-metric cameras and a Position and Orientation System(POS).Unfortunately,the Interior Orientation Parameters(IOPs)of the non-metric cameras are not fixed.Whether the lens distortions are large or small,they effect the image coordinates accordingly.Additionally,Inertial Measurement Units(IMUs)often have observation errors.To address these challenges and improve parameter estimation for UAVs Light Detection and Ranging(LiDAR)and photogrammetry,this paper analyzes the accuracy of POS observations obtained from Global Navigation Satellite System Real Time Kinematic(GNSS-RTK)and IMU data.A method that incorporates additional known conditions for parameter estimation,a series of algorithms to simultaneously solve for IOPs,Exterior Orientation Parameters(EOPs),and camera lens distortion correction parameters are proposed.Extensive experiments demonstrate that the coordinates measured by GNSS-RTK can be directly used as linear EOPs;however,angular EOP measurements from IMUs exhibit relatively large errors compared to adjustment results and require correction during the adjustment process.The IOPs of non-metric cameras vary slightly between images but need to be treated as unknown parameters in high precision applications.Furthermore,it is found that the Ebner systematic error model is sensitive to the choice of the magnification parameter of the photographic baseline length in images,it should be set as less than or equal to one third of the photographic baseline to ensure stable solutions.
文摘多相机三维数字图像相关(three-dimensional digital image correlation,3D-DIC)系统在测量核燃料包壳管应变的实际应用中,多相机标定环节存在坐标系转换引发的累计误差增加及全局优化能力不足等问题。为此,提出一种基于空间标定靶的多相机全局标定方法。首先,提出为各相机在标定靶每个位姿下提供外方位参数初值的方法,保证空间后方交会正确收敛;其次,提出多相机多位姿光束平差(bundle adjustment,BA)方法,保证多相机标定精度达到全局最优。实验结果表明,该方法的标定精度较直接线性变换(direct linear transformation,DLT)方法提高了55.1%,最大位移误差标准差降低了16.3%。同时,该方法无需对标志点进行手动编号,使标定过程实现了自动化,标定效率更高。
