The article presents a methodology for transitioning to the Amsterdam height system based on utilizing global and regional geoid/quasi-geoid models.The study was conducted for the Polish-Ukrainian cross-border sector ...The article presents a methodology for transitioning to the Amsterdam height system based on utilizing global and regional geoid/quasi-geoid models.The study was conducted for the Polish-Ukrainian cross-border sector and expanded to the entire territory of Poland and Ukraine.The input data comprised two regional and five global geoid/quasi-geoid models.The initial data analysis was conducted for all models relative to GNSS/leveling data in the Baltic height system.The secondary analysis was performed relative to the combined PL-quasi-geoid2021 model and the gravimetric EGG2015 model.Based on the analysis results,a methodology for optimizing heights between regional and global geoid/quasi-geoid models was developed,including the following stages:calculation of conditional global and regional geoid/quasi-geoid heights,calculation of approximately predicted height differences between the conditional regional and global geoid/quasi-geoid,implementation of the refinement(correction)of approximate heights at the regional model,optimization of approximate heights at the regional model,and calculation of a regional combined model in the Amsterdam height system.The developed methodology enables the integration of regional and global geoid/quasi-geoid models into the Amsterdam height system with an accuracy of 1-2 cm by optimizing their heights.The advantage of this methodology is that it requires only a minimal amount of GNSS/leveling data to establish connections between different height systems.展开更多
Antarctic clouds and their vertical structures play a significant role in influencing the regional radiation budget and ice mass balance;however,substantial uncertainties persist.Continuous monitoring and research are...Antarctic clouds and their vertical structures play a significant role in influencing the regional radiation budget and ice mass balance;however,substantial uncertainties persist.Continuous monitoring and research are essential for enhancing our understanding of these clouds.This study presents an analysis of cloud occurrence frequency and cloud-base heights(CBHs)at Zhongshan Station in East Antarctica for the first time,utilizing data from a C12 ceilometer covering the period from January 2022 to December 2023.The findings indicate that low clouds dominate at Zhongshan Station,with an average cloud occurrence frequency of 75%.Both the cloud occurrence frequency and CBH distribution exhibit distinct seasonal variations.Specifically,the cloud occurrence frequency during winter is higher than that observed in summer,while winter clouds can develop to greater heights.Over the Southern Ocean,the cloud occurrence frequency during summer surpasses that at Zhongshan Station,with clouds featuring lower CBHs and larger extinction coefficients.Furthermore,it is noteworthy that CBHs derived from the ceilometer are basically consistent with those obtained from radiosondes.Importantly,ERA5 demonstrates commendable performance in retrieving CBHs at Zhongshan Station when compared with ceilometer measurements.展开更多
Plant height(PH),primary lateral branch length(PBL),and branch number(BN)are architectural components impacting peanut pod yield,biomass production,and adaptivity to mechanical harvesting.In this study,a recombinant i...Plant height(PH),primary lateral branch length(PBL),and branch number(BN)are architectural components impacting peanut pod yield,biomass production,and adaptivity to mechanical harvesting.In this study,a recombinant inbred population consisting of 181 individual lines was used to determine genetic controls of PH,PBL,and BN across three environments.Phenotypic data collected from the population demonstrated continuous distributions and transgressive segregation patterns.Broad-sense heritability of PH,PBL,and BN was found to be 0.87,0.88,and 0.92,respectively.Unconditional individual environmental analysis revealed 35 additive QTLs with phenotypic variation explained(PVE)ranging from 4.57 to 21.68%.A two-round meta-analysis resulted in 24consensus and 19 unique QTLs.Five unique QTLs exhibited pleiotropic effects and their genetic bases(pleiotropy or tight linkage)were evaluated.A joint analysis was performed to estimate the QTL by environment interaction(QEI)effects on PH,PBL,and BN,collectively explaining phenotypic variations of 10.80,11.02,and 7.89%,respectively.We identified 3 major and stable QTL regions(uq9-3,uq10-2,and uq16-1)on chromosomes 9,10,and 16,spanning1.43-1.53 Mb genomic regions.Candidate genes involved in phytohormones biosynthesis,signaling,and cell wall development were proposed to regulate these morphological traits.These results provide valuable information for further genetic studies and the development of molecular markers applicable to peanut architecture improvement.展开更多
The mining height of a coal seam is a critical factor influencing the detachment,collapse,and formation of the collapse angle of the strata during strata movement.To clarify the mechanism by which mining height affect...The mining height of a coal seam is a critical factor influencing the detachment,collapse,and formation of the collapse angle of the strata during strata movement.To clarify the mechanism by which mining height affects strata movement characteristics,a physical model experiment was conducted based on the geological conditions of the Panel 122104 in Caojiatan Coal Mine in Shaanxi.The experiment examined strata movement at mining heights of 1 m and 10 m,identifying differences in detachment,collapse behavior,and collapse angles under these two conditions.The results indicate the following:Delamination range directly governs collapse patterns,with higher stress concentration accelerating delamination initiation and expanding affected zones.1 m mining height exhibits a“superposed fixed beam”structure with lower strength compared to the“fixed beam+cantilever beam”configuration under 10 m height.A model estimating collapse step shows 9.13%average error.Strata structure dictates collapse angle mechanisms:Pseudo-plastic deformation under 1 m height determines collapse angle through vertical tensile stress boundaries,whereas 10 m height exhibits brittle fracture behavior with collapse angles approximating fracture angles.Periodic collapse volume above working face directly correlates with mine pressure intensity and is positively correlated with the caving step distance,collapse angle,and caving range.These parameters show higher values under 10 m mining height,resulting in more pronounced mine pressure manifestations compared to 1 m conditions.展开更多
This article analyzes the design of a variable-height simply supported steel truss bridge based on an actual project.It includes its basic situation,introduction to variable-height simply supported steel truss bridges...This article analyzes the design of a variable-height simply supported steel truss bridge based on an actual project.It includes its basic situation,introduction to variable-height simply supported steel truss bridges,key design points of such bridges,and finite element analysis of the design effect.The analysis shows that for such bridges,reasonable main structure design and node design are the keys to determining the overall design idea,and through the reasonable application of the finite element analysis method,the design effect can be scientifically determined,providing a reference for the subsequent structural design of such projects.展开更多
Accurately forecasting the triple point(TP)path is essential for analyzing blast loads and assessing the destructive effectiveness of the height of burst explosion.Empirical models that describe the TP path under norm...Accurately forecasting the triple point(TP)path is essential for analyzing blast loads and assessing the destructive effectiveness of the height of burst explosion.Empirical models that describe the TP path under normal temperature and pressure environments are commonly employed;however,in certain configurations,such as at high-altitudes(HAs),the environment may involve low temperature and pressure conditions.The present study develops a theoretical prediction model for the TP path under reduced pressure and temperature conditions,utilizing the image bursts method,reflected polar analysis,and dimensional analysis.The model's accuracy is evaluated through numerical simulations and experimental data.Results indicate that the prediction model effectively evaluates the TP path under diminished temperature and pressure conditions,with most predictions falling within a±15%deviation.It was found that the TP height increases with altitude.As the altitude rises from 0 m to 10,000 m,the average TP height increases by 61.7%,87.9%,109.0%,and 134.3%for the scaled height of burst of 1.5 m,2.0 m,2.5 m,and 3.0 m,respectively.Moreover,the variation in TP height under HA environments closely mirrors that observed under corresponding reduced pressure conditions.In HA environments,only the effect of low-pressure conditions on the TP path needs to be considered,as the environmental lowtemperature has a minimal effect.展开更多
Plant height is an important trait that affects the crop yield and overall productivity.The Green Revolution,which began in the 1960s,brought about a remarkable surge in grain production,largely credited to the introd...Plant height is an important trait that affects the crop yield and overall productivity.The Green Revolution,which began in the 1960s,brought about a remarkable surge in grain production,largely credited to the introduction of new wheat(Triticum aestivum)and rice(Oryza sativa)varieties,specifically the dwarf variants.Short plants offer several advantages,including denser planting,resistance to lodging,and easier application of fertilizers or fungicides(Stokstad,2023).展开更多
Highly accurate international height reference frames with long-term stability,global consistency,and homogeneity are crucial for monitoring sea level variations,understanding climate change,managing disasters,and sup...Highly accurate international height reference frames with long-term stability,global consistency,and homogeneity are crucial for monitoring sea level variations,understanding climate change,managing disasters,and supporting other applications that benefit scientific research and societal well-being.Currently,there are over 100 local height reference systems worldwide.Unifying these systems is a pivotal step toward constructing international height reference frames.The method introduced in this study-the gravity frequency shift via Satellite Frequency Signal Transfer(SFST)-represents a groundbreaking relativistic geodetic approach,demonstrating its potential to surpass the constraints of conventional techniques.The advent of high-precision optical atomic clocks(OAC)with an accuracy level of 1×10^(-18) has facilitated this method's implementation.The International Association of Geodesy(IAG)has established the International Height Reference System(IHRS)and its practical realization,the International Height Reference Frame(IHRF).Our study focuses on two neighbouring height systems:the China Height System(CHS)and the Nepal Height System(NHS),separated by the Himalayas and the Xizang plateau.We aim to unify these two systems by determining the geopotential and orthometric height differences between their respective height datum stations:the Qingdao Height Datum Station(QHDS)and the Madar Height Datum Station(MHDS)using a simulation experiment with the method mentioned above.Using an OAC with an accuracy of 1×10^(-18),we identified a geopotential difference of-8.348±0.464 m^(2)s^(-2) and an orthometric height difference of 0.786±0.047 m between QHDS and MHDS.These results suggest that the introduced method could unify any two height systems with fewcentimeter-level precision,emphasizing its significance in contributing to the construction of the IHRS/IHRF with today's required precision.In summary,the SFST technique is a novel geodetic method that offers an alternative for height system unification,delivering centimeter-level precision,surpassing traditional methods,and supporting the development of the IHRF.展开更多
Timely identification and forecast of maize tasseling date(TD)are very important for agronomic management,yield prediction,and crop phenotype estimation.Remote sensing-based phenology monitoring has mostly relied on t...Timely identification and forecast of maize tasseling date(TD)are very important for agronomic management,yield prediction,and crop phenotype estimation.Remote sensing-based phenology monitoring has mostly relied on time series spectral index data of the complete growth season.A recent development in maize phenology detection research is to use canopy height(CH)data instead of spectral indices,but its robustness in multiple treatments and stages has not been confirmed.Meanwhile,because data of a complete growth season are needed,the need for timely in-season TD identification remains unmet.This study proposed an approach to timely identify and forecast the maize TD.We obtained RGB and light detection and ranging(Li DAR)data using the unmanned aerial vehicle platform over plots of different maize varieties under multiple treatments.After CH estimation,the feature points(inflection point)from the Logistic curve of the CH time series were extracted as TD.We examined the impact of various independent variables(day of year vs.accumulated growing degree days(AGDD)),sensors(RGB and Li DAR),time series denoise methods,different feature points,and temporal resolution on TD identification.Lastly,we used early CH time series data to predict height growth and further forecast TD.The results showed that using the 99th percentile of plot scale digital surface model and the minimum digital terrain model from Li DAR to estimate maize CH was the most stable across treatments and stages(R~2:0.928 to0.943).For TD identification,the best performance was achieved by using Li DAR data with AGDD as the independent variable,combined with the knee point method,resulting in RMSE of 2.95 d.The high accuracy was maintained at temporal resolutions as coarse as 14 d.TD forecast got more accurate as the CH time series extended.The optimal timing for forecasting TD was when the CH exceeded half of its maximum.Using only Li DAR CH data below 1.6 m and empirical growth rate estimates,the forecasted TD showed an RMSE of 3.90 d.In conclusion,this study exploited the growth characteristics of maize height to provide a practical approach for the timely identification and forecast of maize TD.展开更多
With the advantage of high light intensity due to low scatting, structural colors generated by metallic diffraction nanograting structures, used as a type of diffractive optical element, have shown great potential for...With the advantage of high light intensity due to low scatting, structural colors generated by metallic diffraction nanograting structures, used as a type of diffractive optical element, have shown great potential for application in industrial and scientific research fields such as optical anti-counterfeiting and sensors. Within the visible light wavelength range, the diffraction performance is highly dependent on the height and shape consistencies of the nanograting. However, there is still room for the improvement in the flexible control over structure formation through mechanical nanomachining within this scale. The novelty of this paper lies in proposing a machining strategy for nanograting structures with variable heights through precise regulation of the revolving trajectory using tip-based nano down-milling. It explores how different geometric features of trajectories impact the amount of material deformed into a grating and its distribution shape, referred to as undeformed grating area. By analyzing the forming mechanisms of nanogratings under various trajectories with finite element simulation, the desired undeformed grating area is successfully achieved, which is mainly extruded by the tip flank face to form the right facet of the grating, resulting in a small deformation degree and a high deformation efficiency. Three distinct types of revolving trajectories are filtered out according to five quantitative evaluation indicators for machining performance, namely material plastic deformation, grating profile consistency, grating height consistency, machining forces, and area transforming height, and then are compared in processing nanogratings with different heights. It is obtained that only by regulating the vertical vibration amplitude of the revolving trajectory, the semicircle trajectory with the optimal geometric features has the ability to machine high-quality nanograting structures with a continuous height variation of up to 220 nm in a spacing of 400 nm.展开更多
This study analyzed 10 years of sounding data from Yongxing Island to characterize temperature,humidity,and wind profiles in the atmospheric boundary layer(ABL).Our key findings are as follows.(1)Relative humidity inv...This study analyzed 10 years of sounding data from Yongxing Island to characterize temperature,humidity,and wind profiles in the atmospheric boundary layer(ABL).Our key findings are as follows.(1)Relative humidity inversions(RIs)were the most frequent events(99.8%),followed by surface-based temperature inversions(SBIs,63%),elevated temperature inversions(EIs,50%),and low-level jets(LLJs,41%).(2)Higher near-surface temperature leads to a decrease in EI height,thickness,and intensity.(3)When EIs occurred,RIs were consistently observed beneath the base of the EIs.(4)The intensity of the RIs correlated negatively with surface humidity,whereas the intensity of the LLJs correlated positively with surface winds except in summer.(5)The boundary layer heights(BLHs)are best estimated using the potential temperature gradient method when EIs occur,otherwise,the Richardson number method is the best method.In contrast,the relative humidity and temperature gradient methods exhibit high dispersion or uncertainty.(6)The BLHs showed seasonal variability,peaking in winter(350–1450 m).These findings advance our understanding of ABL dynamics and BLH estimation over tropical islands.展开更多
Vertical jump height is a fundamental measure of neuromuscular power in sports science.A diverse array of measurement instruments is available,yet selecting the appropriate technology requires a nuanced understanding ...Vertical jump height is a fundamental measure of neuromuscular power in sports science.A diverse array of measurement instruments is available,yet selecting the appropriate technology requires a nuanced understanding of the trade-offs between accuracy,cost,and practicality.This comprehensive technical review synthesizes the current state of vertical jump instrumentation.We systematically analyze four primary methodologies:direct measurement,motion capture(kinematic),force platform(kinetic),and flight time-based systems.The underlying technical principles,error sources,and practical limitations of each are detailed.Our analysis reveals a clear hierarchy:force platforms and motion capture systems provide gold-standard accuracy(e.g.,±0.3 cm for force platforms)but are constrained by high cost and laboratory environments.Conversely,flight time-based systems and smartphone applications offer excellent portability and accessibility but are subject to systematic errors(1-4 cm overestimation)and lower temporal resolution.Furthermore,we examine how emerging technologies,including artificial intelligence and wearable sensors,are poised to bridge the gap between laboratory-grade accuracy and field-based utility.This review provides engineers and sports scientists with a consolidated framework to guide instrument selection,data interpretation,and future innovation in athletic performance assessment.展开更多
Accurate,reliable,and regularly updated information is necessary for targeted management of forest stands.This information is usually obtained from sample-based field inventory data.Due to the time-consuming and costl...Accurate,reliable,and regularly updated information is necessary for targeted management of forest stands.This information is usually obtained from sample-based field inventory data.Due to the time-consuming and costly procedure of forest inventory,it is imperative to generate and use the resulting data optimally.Integrating field inventory information with remote sensing data increases the value of field approaches,such as national forest inventories.This study investigated the optimal integration of forest inventory data with aerial image-based canopy height models(CHM)for forest growing stock estimation.For this purpose,fixed-area and angle-count plots from a forest area in Austria were used to assess which type of inventory system is more suitable when the field data is integrated with aerial image analysis.Although a higher correlation was observed between remotely predicted growing stocks and field inventory values for fixed-area plots,the paired t-test results revealed no statistical difference between the two methods.The R2 increased by 0.08 points and the RMSE decreased by 7.7 percentage points(24.8m^(3)·ha^(−1))using fixed-area plots.Since tree height is the most critical variable essential for modeling forest growing stock using aerial images,we also compared the tree heights obtained from CHM to those from the typical field inventory approach.The result shows a high correlation(R^(2)=0.781)between the tree heights extracted from the CHM and those measured in the field.However,the correlation decreased by 0.113 points and the RMSE increased by 4.2 percentage points(1.04m)when the allometrically derived tree heights were analyzed.Moreover,the results of the paired t-test revealed that there is no significant statistical difference between the tree heights extracted from CHM and those measured in the field,but there is a significant statistical difference when the CHM-derived and the allometrically-derived heights were compared.This proved that image-based CHM can obtain more accurate tree height information than field inventory estimations.Overall,the results of this study demonstrated that image-based CHM can be integrated into the forest inventory data at large scales and provide reliable information on forest growing stock.The produced maps reflect the variability of growth conditions and developmental stages of different forest stands.This information is required to characterize the status and changes,e.g.,in forest structure diversity,parameters for volume,and can be used for forest aboveground biomass estimation,which plays an important role in managing and controlling forest resources in mid-term forest management.This is of particular interest to forest managers and forest ecologists.展开更多
Rib spalling is a highly severe issue during mining in deep-buried large-mining-height working faces.This study takes Zhaogu No.2 Coal Mine in Jiaozuo Coalfield,China,as the research background and carries out three f...Rib spalling is a highly severe issue during mining in deep-buried large-mining-height working faces.This study takes Zhaogu No.2 Coal Mine in Jiaozuo Coalfield,China,as the research background and carries out three focused works to address this problem.Firstly,field measurements were conducted to clarify rib spalling characteristics:the coal wall is dominated by shear failure,internal cracks are mainly distributed 3–6 m above the coal wall surface,and the maximum depth of crack development reaches 3 m.Secondly,Universal Distinct Element Code(UDEC)numerical simulation software was used to build a rib spalling model,with the Trigon model adopted to divide the coal wall into blocks.Analysis of four key factors shows that increased buried depth and mining height significantly raise the total length of coal wall internal cracks,increasing rib spalling risk,while higher coal body strength and support strength effectively alleviate this phenomenon.Finally,an orthogonal experiment was designed to quantitatively determine the influence degree of the four factors on rib spalling.Results show that coal body strength has the greatest impact,followed by support strength,mining height,and mining depth in order of influence.This study provides valuable theoretical guidance for on-site prevention and control of coal wall rib spalling.展开更多
To investigate the influence of non-uniform water distribution on the mechanical properties and failure behavior of red sandstone,we designed five immersion heights and durations to achieve varying non-uniform water d...To investigate the influence of non-uniform water distribution on the mechanical properties and failure behavior of red sandstone,we designed five immersion heights and durations to achieve varying non-uniform water distribution states.Uniaxial compression tests were conducted on red sandstone under these conditions.The effects of non-uniform water distribution on deformation,failure,strength,and energy characteristics of red sandstone were analyzed.The impact of non-uniform water distribution on the intensity of rock failure was discussed,and the failure mechanism under non-uniform water distribution was revealed.The hazards of low immersion heights on underground rock structures were analyzed.The results demonstrate that peak strength and elastic modulus of red sandstone exhibit high sensitivity to immersion height,with reductions of 38%and 23%respectively even at L=1/50H.Water immersion reduces both energy storage capacity and energy dissipation capability of red sandstone.The immersion height and duration influence the failure mode of red sandstone by controlling the migration and separation of dry-wet interfaces.Low immersion height poses significant risks to underground rock structures(e.g.,a 38%strength reduction when L=1/50H),and the concentration degree of water non-uniform distribution is the key factor in assessing the weakening effect of water on rocks.展开更多
This article delves Chern's conjecture for hypersurfaces with constant second fundamental form squared length S in the spherical space.At present,determining whether the third gap point of S is 2n remains unsolved...This article delves Chern's conjecture for hypersurfaces with constant second fundamental form squared length S in the spherical space.At present,determining whether the third gap point of S is 2n remains unsolved yet.First,we investigate the height functions and their properties of the position vector and normal vector in natural coordinate vectors,and then prove the existence of a Simons-type integral formula on the hypersurface that simultaneously includes the first,second,and third gap point terms of S.These results can provide new avenues of thought and methods for solving Chern's conjecture.展开更多
In Earth system modeling,the land surface is coupled with the atmosphere through surface turbulent fluxes.These fluxes are computed using mean meteorological variables between the surface and a reference height in the...In Earth system modeling,the land surface is coupled with the atmosphere through surface turbulent fluxes.These fluxes are computed using mean meteorological variables between the surface and a reference height in the atmosphere.However,the dependence of flux computation on the reference height,which is usually set as the lowest level in the atmosphere in Earth system models,has not received much attention.Based on high-resolution large-eddy simulation(LES)data under unstable conditions,we find the setting of reference height is not trivial within the framework of current surface layer theory.With a reasonable prescription of aerodynamic roughness length(following the setting in LESs),reference heights near the top of the surface layer tend to provide the best estimate of surface fluxes,especially for the momentum flux.Furthermore,this conclusion for the sensible heat flux is insensitive to the ratio of roughness length for momentum versus heat.These results are robust,whether using the classical or revised surface layer theory.They provide a potential guide for setting the proper reference heights for Earth system modeling and can be further tested in the near future using observational data from land–atmosphere feedback observatories.展开更多
Recently,information acquired at the canopy top,such as spectral and textural data,has been widely used to estimate plant nitrogen(N)accumulation(PNA).The response of crops to N uptake involves not only changes in hor...Recently,information acquired at the canopy top,such as spectral and textural data,has been widely used to estimate plant nitrogen(N)accumulation(PNA).The response of crops to N uptake involves not only changes in horizontal canopy top information but also an increase in vertical plant height(PH).It remains unclear whether the fusion of spectral indices with PH can improve the estimation performance of PNA models based on spectral remote sensing across different growth stages.展开更多
Hydraulic fracturing and commingle production of multiple layers are extensively adopted in unconventional tight gas reservoirs.Accurate determination of parameters of individual layers in multilayered tight gas reser...Hydraulic fracturing and commingle production of multiple layers are extensively adopted in unconventional tight gas reservoirs.Accurate determination of parameters of individual layers in multilayered tight gas reservoirs is essential for well performance evaluation and development strategy optimization.However,most analytical models for fractured vertical wells in stratified gas reservoirs focus on fully penetrated hydraulic fractures,neglecting the influence of partial penetration of hydraulic fractures.This paper presents a semi-analytical model to investigate the transient pressure behavior of vertically fractured wells in dual porosity multi-layered tight gas reservoirs.The partial penetration of hydraulic fracture,the vertical heterogeneities of layer properties,the differences between hydraulic fracture lengths in each layer and the stress sensitivity are all incorporated in the proposed model.The point-source solution,Laplace transformation,Fourier transformation,Pedrosa's transformation,perturbation technique,and the superposition principle are applied to obtain the analytical solution of transient pressure responses.The proposed model is validated against a commercial software,and the transient pressure behavior of vertically fractured wells in multi-layered tight gas reservoirs are analyzed.Based on the characteristics of the type curves,seven flow regimes can be identified,including wellbore storage,transitional flow period,reservoir linear flow period,vertical pseudo-radial flow in fracture system,inter-porosity flow period,late-time pseudo-radial flow period,and the boundary-dominated flow period.Sensitivity analyses reveal that the penetration ratio of hydraulic fracture has primary influence on early-time transient pressure behavior and production contribution,while the stress sensitivity mainly affects the late-time transient pressure behavior.Gas production at the initial stage is mainly contributed by the high-pressure/high-permeability layer,and gas backflow will occur during initial production stage for obviously unequal initial formation pressures.Finally,two field cases are conducted to illustrate the applicability of the proposed model.The model and corresponding conclusions can provide technical support for performance analysis of tight gas reservoirs.展开更多
Traditional automated guided vehicle(AGV)primarily relies on scheduling systems to manage warehouse locations and execute picking or placing tasks on fixedheight pallets.However,these conventional systems are illsuite...Traditional automated guided vehicle(AGV)primarily relies on scheduling systems to manage warehouse locations and execute picking or placing tasks on fixedheight pallets.However,these conventional systems are illsuited for scenarios involving variable heights,such as vehicle loading and unloading or the complex stacking of soft packages.To address the challenges of AGV endeffector operations in nonfixed height scenarios,this paper proposes an innovative solution leveraging lowcost depth camera sensors.By capturing image and depth data,and integrating deep learning,image processing,and spatial attitude calculation techniques,the method accurately determines the position of the endeffector center point relative to the upper plane of the fork.The approach effectively resolves a key issue in AGV operations within intelligent logistics scenarios that lack fixed heights.The proposed algorithm is deployed on a domestic embedded,lowcost ARM chip controller,and extensive experiments are conducted on a real AGV equipped with multiple stacked vehicles and nonstandard vehicles.The experimental results demonstrate that for diverse vehicles with different heights,the measurement error can be maintained within±10 mm,satisfying the requirements for highprecision measurement.The height measurement method developed in the paper not only enhances the AGV’s adaptability in nonfixed height scenarios but also significantly broadens its application potential across various industries.展开更多
文摘The article presents a methodology for transitioning to the Amsterdam height system based on utilizing global and regional geoid/quasi-geoid models.The study was conducted for the Polish-Ukrainian cross-border sector and expanded to the entire territory of Poland and Ukraine.The input data comprised two regional and five global geoid/quasi-geoid models.The initial data analysis was conducted for all models relative to GNSS/leveling data in the Baltic height system.The secondary analysis was performed relative to the combined PL-quasi-geoid2021 model and the gravimetric EGG2015 model.Based on the analysis results,a methodology for optimizing heights between regional and global geoid/quasi-geoid models was developed,including the following stages:calculation of conditional global and regional geoid/quasi-geoid heights,calculation of approximately predicted height differences between the conditional regional and global geoid/quasi-geoid,implementation of the refinement(correction)of approximate heights at the regional model,optimization of approximate heights at the regional model,and calculation of a regional combined model in the Amsterdam height system.The developed methodology enables the integration of regional and global geoid/quasi-geoid models into the Amsterdam height system with an accuracy of 1-2 cm by optimizing their heights.The advantage of this methodology is that it requires only a minimal amount of GNSS/leveling data to establish connections between different height systems.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFC2802501)the National Natural Science Foundation of China(Grant Nos.42175154 and 42305084)+1 种基金the Hunan Provincial Natural Science Foundation of China(Grant No.2024JJ2058)Research Project of the National University of Defense Technology(Grant No.202401-YJRC-XX-030)。
文摘Antarctic clouds and their vertical structures play a significant role in influencing the regional radiation budget and ice mass balance;however,substantial uncertainties persist.Continuous monitoring and research are essential for enhancing our understanding of these clouds.This study presents an analysis of cloud occurrence frequency and cloud-base heights(CBHs)at Zhongshan Station in East Antarctica for the first time,utilizing data from a C12 ceilometer covering the period from January 2022 to December 2023.The findings indicate that low clouds dominate at Zhongshan Station,with an average cloud occurrence frequency of 75%.Both the cloud occurrence frequency and CBH distribution exhibit distinct seasonal variations.Specifically,the cloud occurrence frequency during winter is higher than that observed in summer,while winter clouds can develop to greater heights.Over the Southern Ocean,the cloud occurrence frequency during summer surpasses that at Zhongshan Station,with clouds featuring lower CBHs and larger extinction coefficients.Furthermore,it is noteworthy that CBHs derived from the ceilometer are basically consistent with those obtained from radiosondes.Importantly,ERA5 demonstrates commendable performance in retrieving CBHs at Zhongshan Station when compared with ceilometer measurements.
基金supported by the Natural Science Foundation of Shandong Province,China(ZR2022MC045)the National Natural Science Foundation of China(32001584,32201876)+2 种基金the Major Science and Technology Program of Xinjiang Uygur Autonomous Region,China(2022A02008-3)the Breeding Project from Department of Science&Technology of Shandong Province,China(2022LZGC007)the Agricultural Scientific and the Technological Innovation Project of Shandong Academy of Agricultural Sciences,China(CXGC2023A06,CXGC2023A39 and CXGC2023A46),and the Major Scientific and Technological Achievements Cultivation Program of Shandong Academy of Agricultural Sciences,China(CXGC2025E02)。
文摘Plant height(PH),primary lateral branch length(PBL),and branch number(BN)are architectural components impacting peanut pod yield,biomass production,and adaptivity to mechanical harvesting.In this study,a recombinant inbred population consisting of 181 individual lines was used to determine genetic controls of PH,PBL,and BN across three environments.Phenotypic data collected from the population demonstrated continuous distributions and transgressive segregation patterns.Broad-sense heritability of PH,PBL,and BN was found to be 0.87,0.88,and 0.92,respectively.Unconditional individual environmental analysis revealed 35 additive QTLs with phenotypic variation explained(PVE)ranging from 4.57 to 21.68%.A two-round meta-analysis resulted in 24consensus and 19 unique QTLs.Five unique QTLs exhibited pleiotropic effects and their genetic bases(pleiotropy or tight linkage)were evaluated.A joint analysis was performed to estimate the QTL by environment interaction(QEI)effects on PH,PBL,and BN,collectively explaining phenotypic variations of 10.80,11.02,and 7.89%,respectively.We identified 3 major and stable QTL regions(uq9-3,uq10-2,and uq16-1)on chromosomes 9,10,and 16,spanning1.43-1.53 Mb genomic regions.Candidate genes involved in phytohormones biosynthesis,signaling,and cell wall development were proposed to regulate these morphological traits.These results provide valuable information for further genetic studies and the development of molecular markers applicable to peanut architecture improvement.
文摘The mining height of a coal seam is a critical factor influencing the detachment,collapse,and formation of the collapse angle of the strata during strata movement.To clarify the mechanism by which mining height affects strata movement characteristics,a physical model experiment was conducted based on the geological conditions of the Panel 122104 in Caojiatan Coal Mine in Shaanxi.The experiment examined strata movement at mining heights of 1 m and 10 m,identifying differences in detachment,collapse behavior,and collapse angles under these two conditions.The results indicate the following:Delamination range directly governs collapse patterns,with higher stress concentration accelerating delamination initiation and expanding affected zones.1 m mining height exhibits a“superposed fixed beam”structure with lower strength compared to the“fixed beam+cantilever beam”configuration under 10 m height.A model estimating collapse step shows 9.13%average error.Strata structure dictates collapse angle mechanisms:Pseudo-plastic deformation under 1 m height determines collapse angle through vertical tensile stress boundaries,whereas 10 m height exhibits brittle fracture behavior with collapse angles approximating fracture angles.Periodic collapse volume above working face directly correlates with mine pressure intensity and is positively correlated with the caving step distance,collapse angle,and caving range.These parameters show higher values under 10 m mining height,resulting in more pronounced mine pressure manifestations compared to 1 m conditions.
文摘This article analyzes the design of a variable-height simply supported steel truss bridge based on an actual project.It includes its basic situation,introduction to variable-height simply supported steel truss bridges,key design points of such bridges,and finite element analysis of the design effect.The analysis shows that for such bridges,reasonable main structure design and node design are the keys to determining the overall design idea,and through the reasonable application of the finite element analysis method,the design effect can be scientifically determined,providing a reference for the subsequent structural design of such projects.
基金funding from Anhui Engineering Laboratory of Explosive Materials and Technology Foundation(No.AHBP2022B-04)Natural Science Research Project of Anhui Educational Committee(No.2023AH051221)+1 种基金Anhui Provincial Natural Science Foundation(No.2208085QA26)Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology for the project related to this work.
文摘Accurately forecasting the triple point(TP)path is essential for analyzing blast loads and assessing the destructive effectiveness of the height of burst explosion.Empirical models that describe the TP path under normal temperature and pressure environments are commonly employed;however,in certain configurations,such as at high-altitudes(HAs),the environment may involve low temperature and pressure conditions.The present study develops a theoretical prediction model for the TP path under reduced pressure and temperature conditions,utilizing the image bursts method,reflected polar analysis,and dimensional analysis.The model's accuracy is evaluated through numerical simulations and experimental data.Results indicate that the prediction model effectively evaluates the TP path under diminished temperature and pressure conditions,with most predictions falling within a±15%deviation.It was found that the TP height increases with altitude.As the altitude rises from 0 m to 10,000 m,the average TP height increases by 61.7%,87.9%,109.0%,and 134.3%for the scaled height of burst of 1.5 m,2.0 m,2.5 m,and 3.0 m,respectively.Moreover,the variation in TP height under HA environments closely mirrors that observed under corresponding reduced pressure conditions.In HA environments,only the effect of low-pressure conditions on the TP path needs to be considered,as the environmental lowtemperature has a minimal effect.
基金supported by grants from the National Natural Science Foundation of China(32270290)the Shanghai Engineering Research Center of Plant Germplasm Resources(17DZ2252700).
文摘Plant height is an important trait that affects the crop yield and overall productivity.The Green Revolution,which began in the 1960s,brought about a remarkable surge in grain production,largely credited to the introduction of new wheat(Triticum aestivum)and rice(Oryza sativa)varieties,specifically the dwarf variants.Short plants offer several advantages,including denser planting,resistance to lodging,and easier application of fertilizers or fungicides(Stokstad,2023).
基金the National Natural Science Foundation of China(NSFC)(Grant Nos.42030105,42274011,42074019,41974034,42204006)。
文摘Highly accurate international height reference frames with long-term stability,global consistency,and homogeneity are crucial for monitoring sea level variations,understanding climate change,managing disasters,and supporting other applications that benefit scientific research and societal well-being.Currently,there are over 100 local height reference systems worldwide.Unifying these systems is a pivotal step toward constructing international height reference frames.The method introduced in this study-the gravity frequency shift via Satellite Frequency Signal Transfer(SFST)-represents a groundbreaking relativistic geodetic approach,demonstrating its potential to surpass the constraints of conventional techniques.The advent of high-precision optical atomic clocks(OAC)with an accuracy level of 1×10^(-18) has facilitated this method's implementation.The International Association of Geodesy(IAG)has established the International Height Reference System(IHRS)and its practical realization,the International Height Reference Frame(IHRF).Our study focuses on two neighbouring height systems:the China Height System(CHS)and the Nepal Height System(NHS),separated by the Himalayas and the Xizang plateau.We aim to unify these two systems by determining the geopotential and orthometric height differences between their respective height datum stations:the Qingdao Height Datum Station(QHDS)and the Madar Height Datum Station(MHDS)using a simulation experiment with the method mentioned above.Using an OAC with an accuracy of 1×10^(-18),we identified a geopotential difference of-8.348±0.464 m^(2)s^(-2) and an orthometric height difference of 0.786±0.047 m between QHDS and MHDS.These results suggest that the introduced method could unify any two height systems with fewcentimeter-level precision,emphasizing its significance in contributing to the construction of the IHRS/IHRF with today's required precision.In summary,the SFST technique is a novel geodetic method that offers an alternative for height system unification,delivering centimeter-level precision,surpassing traditional methods,and supporting the development of the IHRF.
基金supported by National Science and Technology Major Project(2022ZD0115701)Nanfan Special Project,CAAS(YBXM2305,YBXM2401,YBXM2402,PTXM2402)+1 种基金National Natural Science Foundation of China(42071426,42301427)the Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences。
文摘Timely identification and forecast of maize tasseling date(TD)are very important for agronomic management,yield prediction,and crop phenotype estimation.Remote sensing-based phenology monitoring has mostly relied on time series spectral index data of the complete growth season.A recent development in maize phenology detection research is to use canopy height(CH)data instead of spectral indices,but its robustness in multiple treatments and stages has not been confirmed.Meanwhile,because data of a complete growth season are needed,the need for timely in-season TD identification remains unmet.This study proposed an approach to timely identify and forecast the maize TD.We obtained RGB and light detection and ranging(Li DAR)data using the unmanned aerial vehicle platform over plots of different maize varieties under multiple treatments.After CH estimation,the feature points(inflection point)from the Logistic curve of the CH time series were extracted as TD.We examined the impact of various independent variables(day of year vs.accumulated growing degree days(AGDD)),sensors(RGB and Li DAR),time series denoise methods,different feature points,and temporal resolution on TD identification.Lastly,we used early CH time series data to predict height growth and further forecast TD.The results showed that using the 99th percentile of plot scale digital surface model and the minimum digital terrain model from Li DAR to estimate maize CH was the most stable across treatments and stages(R~2:0.928 to0.943).For TD identification,the best performance was achieved by using Li DAR data with AGDD as the independent variable,combined with the knee point method,resulting in RMSE of 2.95 d.The high accuracy was maintained at temporal resolutions as coarse as 14 d.TD forecast got more accurate as the CH time series extended.The optimal timing for forecasting TD was when the CH exceeded half of its maximum.Using only Li DAR CH data below 1.6 m and empirical growth rate estimates,the forecasted TD showed an RMSE of 3.90 d.In conclusion,this study exploited the growth characteristics of maize height to provide a practical approach for the timely identification and forecast of maize TD.
基金financial supports from the National Natural Science Foundation of China(52105434)China Postdoctoral Science Foundation(2022M710642).
文摘With the advantage of high light intensity due to low scatting, structural colors generated by metallic diffraction nanograting structures, used as a type of diffractive optical element, have shown great potential for application in industrial and scientific research fields such as optical anti-counterfeiting and sensors. Within the visible light wavelength range, the diffraction performance is highly dependent on the height and shape consistencies of the nanograting. However, there is still room for the improvement in the flexible control over structure formation through mechanical nanomachining within this scale. The novelty of this paper lies in proposing a machining strategy for nanograting structures with variable heights through precise regulation of the revolving trajectory using tip-based nano down-milling. It explores how different geometric features of trajectories impact the amount of material deformed into a grating and its distribution shape, referred to as undeformed grating area. By analyzing the forming mechanisms of nanogratings under various trajectories with finite element simulation, the desired undeformed grating area is successfully achieved, which is mainly extruded by the tip flank face to form the right facet of the grating, resulting in a small deformation degree and a high deformation efficiency. Three distinct types of revolving trajectories are filtered out according to five quantitative evaluation indicators for machining performance, namely material plastic deformation, grating profile consistency, grating height consistency, machining forces, and area transforming height, and then are compared in processing nanogratings with different heights. It is obtained that only by regulating the vertical vibration amplitude of the revolving trajectory, the semicircle trajectory with the optimal geometric features has the ability to machine high-quality nanograting structures with a continuous height variation of up to 220 nm in a spacing of 400 nm.
基金National Key Research and Development Program of China(2023YFC3008002)National Natural Science Foundation of China(U21A6001,42075059)Key Laboratory of Guangdong Province(2020B1212060025)。
文摘This study analyzed 10 years of sounding data from Yongxing Island to characterize temperature,humidity,and wind profiles in the atmospheric boundary layer(ABL).Our key findings are as follows.(1)Relative humidity inversions(RIs)were the most frequent events(99.8%),followed by surface-based temperature inversions(SBIs,63%),elevated temperature inversions(EIs,50%),and low-level jets(LLJs,41%).(2)Higher near-surface temperature leads to a decrease in EI height,thickness,and intensity.(3)When EIs occurred,RIs were consistently observed beneath the base of the EIs.(4)The intensity of the RIs correlated negatively with surface humidity,whereas the intensity of the LLJs correlated positively with surface winds except in summer.(5)The boundary layer heights(BLHs)are best estimated using the potential temperature gradient method when EIs occur,otherwise,the Richardson number method is the best method.In contrast,the relative humidity and temperature gradient methods exhibit high dispersion or uncertainty.(6)The BLHs showed seasonal variability,peaking in winter(350–1450 m).These findings advance our understanding of ABL dynamics and BLH estimation over tropical islands.
文摘Vertical jump height is a fundamental measure of neuromuscular power in sports science.A diverse array of measurement instruments is available,yet selecting the appropriate technology requires a nuanced understanding of the trade-offs between accuracy,cost,and practicality.This comprehensive technical review synthesizes the current state of vertical jump instrumentation.We systematically analyze four primary methodologies:direct measurement,motion capture(kinematic),force platform(kinetic),and flight time-based systems.The underlying technical principles,error sources,and practical limitations of each are detailed.Our analysis reveals a clear hierarchy:force platforms and motion capture systems provide gold-standard accuracy(e.g.,±0.3 cm for force platforms)but are constrained by high cost and laboratory environments.Conversely,flight time-based systems and smartphone applications offer excellent portability and accessibility but are subject to systematic errors(1-4 cm overestimation)and lower temporal resolution.Furthermore,we examine how emerging technologies,including artificial intelligence and wearable sensors,are poised to bridge the gap between laboratory-grade accuracy and field-based utility.This review provides engineers and sports scientists with a consolidated framework to guide instrument selection,data interpretation,and future innovation in athletic performance assessment.
基金supported by grants provided within the research project»EO4Forest:Use of multi-temporal Sentinel-2 and VHR Pleiades stereo data for sustainable forest monitoring and management«funded by the Austrian Federal Ministry for Climate Action,Environ-ment,Energy,Mobility,Innovation and Technology(BMK)within the FFG Austrian Space Applications Program ASAP 12(grant agreement number 854027).
文摘Accurate,reliable,and regularly updated information is necessary for targeted management of forest stands.This information is usually obtained from sample-based field inventory data.Due to the time-consuming and costly procedure of forest inventory,it is imperative to generate and use the resulting data optimally.Integrating field inventory information with remote sensing data increases the value of field approaches,such as national forest inventories.This study investigated the optimal integration of forest inventory data with aerial image-based canopy height models(CHM)for forest growing stock estimation.For this purpose,fixed-area and angle-count plots from a forest area in Austria were used to assess which type of inventory system is more suitable when the field data is integrated with aerial image analysis.Although a higher correlation was observed between remotely predicted growing stocks and field inventory values for fixed-area plots,the paired t-test results revealed no statistical difference between the two methods.The R2 increased by 0.08 points and the RMSE decreased by 7.7 percentage points(24.8m^(3)·ha^(−1))using fixed-area plots.Since tree height is the most critical variable essential for modeling forest growing stock using aerial images,we also compared the tree heights obtained from CHM to those from the typical field inventory approach.The result shows a high correlation(R^(2)=0.781)between the tree heights extracted from the CHM and those measured in the field.However,the correlation decreased by 0.113 points and the RMSE increased by 4.2 percentage points(1.04m)when the allometrically derived tree heights were analyzed.Moreover,the results of the paired t-test revealed that there is no significant statistical difference between the tree heights extracted from CHM and those measured in the field,but there is a significant statistical difference when the CHM-derived and the allometrically-derived heights were compared.This proved that image-based CHM can obtain more accurate tree height information than field inventory estimations.Overall,the results of this study demonstrated that image-based CHM can be integrated into the forest inventory data at large scales and provide reliable information on forest growing stock.The produced maps reflect the variability of growth conditions and developmental stages of different forest stands.This information is required to characterize the status and changes,e.g.,in forest structure diversity,parameters for volume,and can be used for forest aboveground biomass estimation,which plays an important role in managing and controlling forest resources in mid-term forest management.This is of particular interest to forest managers and forest ecologists.
基金supported by the National Key Research and Development Program of China(No.2023YFC2907501)the National Natural Science Foundation of China(No.52374106)+1 种基金the China Postdoctoral Science Foundation(Grant no.2024T171006)the National Natural Science Foundation of China(Grant no.52204163).
文摘Rib spalling is a highly severe issue during mining in deep-buried large-mining-height working faces.This study takes Zhaogu No.2 Coal Mine in Jiaozuo Coalfield,China,as the research background and carries out three focused works to address this problem.Firstly,field measurements were conducted to clarify rib spalling characteristics:the coal wall is dominated by shear failure,internal cracks are mainly distributed 3–6 m above the coal wall surface,and the maximum depth of crack development reaches 3 m.Secondly,Universal Distinct Element Code(UDEC)numerical simulation software was used to build a rib spalling model,with the Trigon model adopted to divide the coal wall into blocks.Analysis of four key factors shows that increased buried depth and mining height significantly raise the total length of coal wall internal cracks,increasing rib spalling risk,while higher coal body strength and support strength effectively alleviate this phenomenon.Finally,an orthogonal experiment was designed to quantitatively determine the influence degree of the four factors on rib spalling.Results show that coal body strength has the greatest impact,followed by support strength,mining height,and mining depth in order of influence.This study provides valuable theoretical guidance for on-site prevention and control of coal wall rib spalling.
基金supported by the National Natural Science Foundation of China(Nos.52474133,52304227,52304091,and 52374095)the Natural Science Foundation of Hunan Province(Nos.2025JJ50316 and 2023JJ40548).
文摘To investigate the influence of non-uniform water distribution on the mechanical properties and failure behavior of red sandstone,we designed five immersion heights and durations to achieve varying non-uniform water distribution states.Uniaxial compression tests were conducted on red sandstone under these conditions.The effects of non-uniform water distribution on deformation,failure,strength,and energy characteristics of red sandstone were analyzed.The impact of non-uniform water distribution on the intensity of rock failure was discussed,and the failure mechanism under non-uniform water distribution was revealed.The hazards of low immersion heights on underground rock structures were analyzed.The results demonstrate that peak strength and elastic modulus of red sandstone exhibit high sensitivity to immersion height,with reductions of 38%and 23%respectively even at L=1/50H.Water immersion reduces both energy storage capacity and energy dissipation capability of red sandstone.The immersion height and duration influence the failure mode of red sandstone by controlling the migration and separation of dry-wet interfaces.Low immersion height poses significant risks to underground rock structures(e.g.,a 38%strength reduction when L=1/50H),and the concentration degree of water non-uniform distribution is the key factor in assessing the weakening effect of water on rocks.
文摘This article delves Chern's conjecture for hypersurfaces with constant second fundamental form squared length S in the spherical space.At present,determining whether the third gap point of S is 2n remains unsolved yet.First,we investigate the height functions and their properties of the position vector and normal vector in natural coordinate vectors,and then prove the existence of a Simons-type integral formula on the hypersurface that simultaneously includes the first,second,and third gap point terms of S.These results can provide new avenues of thought and methods for solving Chern's conjecture.
基金supported by the Natural Science Foundation of China(Grant Nos.42088101 and 42375163)the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2021B0301030007)the specific research fund of The Innovation Platform for Academicians of Hainan Province(Grant No.YSPTZX202143)。
文摘In Earth system modeling,the land surface is coupled with the atmosphere through surface turbulent fluxes.These fluxes are computed using mean meteorological variables between the surface and a reference height in the atmosphere.However,the dependence of flux computation on the reference height,which is usually set as the lowest level in the atmosphere in Earth system models,has not received much attention.Based on high-resolution large-eddy simulation(LES)data under unstable conditions,we find the setting of reference height is not trivial within the framework of current surface layer theory.With a reasonable prescription of aerodynamic roughness length(following the setting in LESs),reference heights near the top of the surface layer tend to provide the best estimate of surface fluxes,especially for the momentum flux.Furthermore,this conclusion for the sensible heat flux is insensitive to the ratio of roughness length for momentum versus heat.These results are robust,whether using the classical or revised surface layer theory.They provide a potential guide for setting the proper reference heights for Earth system modeling and can be further tested in the near future using observational data from land–atmosphere feedback observatories.
基金supported by the National Key Research and Development Plan Project Sub-Topic of China(Grant Nos.2022YFD1901500 and 2022YFD1901505-07)the National Natural Science Foundation of China(Grant No.32260531)+1 种基金the Key Laboratory of Molecular Breeding for Grain and Oil Crops in Guizhou Province,China(Grant No.Qiankehezhongyindi[2023]8)the Key Laboratory of Functional Agriculture of Guizhou Provincial Higher Education Institutions,China(Grant No.Qianjiaoji[2023]007).
文摘Recently,information acquired at the canopy top,such as spectral and textural data,has been widely used to estimate plant nitrogen(N)accumulation(PNA).The response of crops to N uptake involves not only changes in horizontal canopy top information but also an increase in vertical plant height(PH).It remains unclear whether the fusion of spectral indices with PH can improve the estimation performance of PNA models based on spectral remote sensing across different growth stages.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174036,52234003)the Sichuan Province Science and Technology Program(Grant No.2024NSFSC0199)the Joint Fund for Innovation and Development of Chongqing Natural Science Foundation(Grant No.2023NSCQ-LZX0184).
文摘Hydraulic fracturing and commingle production of multiple layers are extensively adopted in unconventional tight gas reservoirs.Accurate determination of parameters of individual layers in multilayered tight gas reservoirs is essential for well performance evaluation and development strategy optimization.However,most analytical models for fractured vertical wells in stratified gas reservoirs focus on fully penetrated hydraulic fractures,neglecting the influence of partial penetration of hydraulic fractures.This paper presents a semi-analytical model to investigate the transient pressure behavior of vertically fractured wells in dual porosity multi-layered tight gas reservoirs.The partial penetration of hydraulic fracture,the vertical heterogeneities of layer properties,the differences between hydraulic fracture lengths in each layer and the stress sensitivity are all incorporated in the proposed model.The point-source solution,Laplace transformation,Fourier transformation,Pedrosa's transformation,perturbation technique,and the superposition principle are applied to obtain the analytical solution of transient pressure responses.The proposed model is validated against a commercial software,and the transient pressure behavior of vertically fractured wells in multi-layered tight gas reservoirs are analyzed.Based on the characteristics of the type curves,seven flow regimes can be identified,including wellbore storage,transitional flow period,reservoir linear flow period,vertical pseudo-radial flow in fracture system,inter-porosity flow period,late-time pseudo-radial flow period,and the boundary-dominated flow period.Sensitivity analyses reveal that the penetration ratio of hydraulic fracture has primary influence on early-time transient pressure behavior and production contribution,while the stress sensitivity mainly affects the late-time transient pressure behavior.Gas production at the initial stage is mainly contributed by the high-pressure/high-permeability layer,and gas backflow will occur during initial production stage for obviously unequal initial formation pressures.Finally,two field cases are conducted to illustrate the applicability of the proposed model.The model and corresponding conclusions can provide technical support for performance analysis of tight gas reservoirs.
基金Supported by the Key Research and Development Program of Anhui Province(No.201904a05020035)the Postdoctoral Research Initiative of Anhui Province(No.2024B804)the Hefei City Key Technology Research and Development‘Ranking’(No.2023SGJ017).
文摘Traditional automated guided vehicle(AGV)primarily relies on scheduling systems to manage warehouse locations and execute picking or placing tasks on fixedheight pallets.However,these conventional systems are illsuited for scenarios involving variable heights,such as vehicle loading and unloading or the complex stacking of soft packages.To address the challenges of AGV endeffector operations in nonfixed height scenarios,this paper proposes an innovative solution leveraging lowcost depth camera sensors.By capturing image and depth data,and integrating deep learning,image processing,and spatial attitude calculation techniques,the method accurately determines the position of the endeffector center point relative to the upper plane of the fork.The approach effectively resolves a key issue in AGV operations within intelligent logistics scenarios that lack fixed heights.The proposed algorithm is deployed on a domestic embedded,lowcost ARM chip controller,and extensive experiments are conducted on a real AGV equipped with multiple stacked vehicles and nonstandard vehicles.The experimental results demonstrate that for diverse vehicles with different heights,the measurement error can be maintained within±10 mm,satisfying the requirements for highprecision measurement.The height measurement method developed in the paper not only enhances the AGV’s adaptability in nonfixed height scenarios but also significantly broadens its application potential across various industries.
