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The effect of topographic density variations on the geoid and orthometric heights in Hong Kong

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Geodesy and Geodynamics 2024年第5期15卷 495-503页

作者： Albertini Nsiah Ababio department of land Surveying and Geo-Informatics Hong Kong Polytechnic UniversityHong KongChina

Utilizing the adopted average topographic density of 2670 kg/m^(3)in the reduction of gravity anomalies introduces errors attributed to topographic density variations,which consequently affect geoid modeling ***,the mean gravity along the plumbline within the topography in the definition of Helmert orthometric heights is computed approximately by applying the Poincar e-Prey gravity reduction where the topographic density variations are *** Helmert orthometric heights of benchmarks are then affected by *** errors could be random or systematic depending on the specific geological setting of the region where the leveling network is physically established and/or the geoid model is *** example of systematic errors in orthometric heights can be given for large regions characterized by sediment or volcanic deposits,the density of which is substantially lower than the adopted topographic density used in Helmert's definition of *** same applies to geoid modeling *** this study,we investigate these errors in the Hong Kong territory,where topographic density is about 20%lower than the density of 2670 kg/m^(3).We use the digital rock density model to estimate the effect of topographic density variations on the geoid and orthometric *** results show that this effect on the geoid and Helmert orthometric heights reach maxima of about 2.1 and 0.5 cm,*** results provide clear evidence that rock density models are essential in physical geodesy applications involving gravimetric geoid modeling and orthometric height determination despite some criticism that could be raised regarding the reliability of these density ***,in regions dominated by sedimentary and igneous rocks,the geological information is essential in these applications because topographic densities are substantially lower than the average density of 2670 kg/m^(3),thus introducing large systematic errors in geoid and orthometric

关键词： Rock density Geoid Topography Heights Leveling network

Elevational distribution of forests and its spatiotemporal dynamics in subtropical China from 2000 to 2019

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Science China Earth Sciences 2024年第8期67卷 2563-2582页

作者： Zhencan ZHENG Liuwen ZHUANG Guofang MIAO Han LIU Zhiqiang CHENG Wenyu LI Rong SHANG Peng GONG Jing Ming CHEN Institute of Geography Fujian Normal University Key Laboratory of Humid Subtropical Eco-Geographical Process (Ministry of Education) Fujian Normal University School of Geographical Sciences Fujian Normal University National land Consolidation Center Ministry of Natural Resources Key Laboratory of land Consolidation and Rehabilitation Ministry of Natural Resources Key Laboratory of Digital Mapping and land Information Application Ministry of Natural Resources department of Geography & Planning University of Toronto department of Geography The University of Hong Kong

The subtropical region of China possesses abundant forest resources and features a mountainous *** the implementation of policies such as natural forest protection,the Grain for Green Project,and other initiatives since the beginning of the 21st century,coupled with climate change,the forest resources in this region have undergone significant changes compared to historical *** addition,forest resources distributing mainly in mountainous areas also implies that these changes may vary significantly with *** explore the spatiotemporal dynamics of forest distribution in subtropical China since 2000,especially the trend of changes with elevation,we analyzed the data from two land cover products focusing on forest cover and forest *** used a hierarchical approach,in which coarse-classification forest cover data with relatively small uncertainties impose constraints on forest type data with larger uncertainties,to achieve a reasonable balance between obtaining more details and reducing data *** first divided the forest cover data into‘unchanged'and‘changed'*** the constraints by the forest cover results,we further analyzed the‘unchanged'and‘changed'forest *** results indicated that,since the implementation of ecological engineering and management policies,54%of the area in the subtropical region had maintained unchanged forest cover attributes over the past 20 years,which implied the good state of ecological *** results also showed that dynamic conversions existed in the long term between forests and lands for essential production needs like *** elevational variations of forest cover suggested that the dominant changes came from the conversion between forests and croplands in low-elevation regions below 700 m,the conversion between forests and shrublands in mid-elevation regions of 700–1500 m,and the conversion between forests and grasslands in high-elevation regions above 2000 *** the regio

关键词： Subtropical China land cover Forest cover Forest type Elevational distribution

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Dewatering of Scenedesmus obliquus Cultivation Substrate with Microfiltration:Potential and Challenges for Water Reuse and Effective Harvesting

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Engineering 2024年第7期38卷 155-163页

作者： Marco Malaguti Lorenzo Craveri Francesco Ricceri Vincenzo Riggio Mariachiara Zanetti Alberto Tiraferri department of Environment Land and Infrastructure EngineeringPolitecnico di TorinoTorino 10129Italy Clean Water Center Politecnico di TorinoTorino 10129Italy

In the microalgae harvesting process,which includes a step for dewatering the algal suspension,directly reusing extracted water in situ would decrease the freshwater footprint of cultivation *** various algae harvesting techniques,membrane-based filtration has shown numerous *** study evaluated the reuse of permeate streams derived from Scenedesmus obliquus(***)biomass filtration under bench-scale and pilot-scale *** particular,this study identified a series of challenges and mechanisms that influence the water reuse potential and the robustness of the membrane harvesting *** a preliminary phase of this investigation,the health status of the initial biomass was found to have important implications for the harvesting performance and quality of the permeate stream to be reused;healthy biomass ensured better dewatering performance(i.e.,higher water fluxes)and higher quality of the permeate water streams.A series of bench-scale filtration experiments with different combinations of cross-flow velocity and pressure values were performed to identify the operative conditions that would maximize water *** selected conditions,2.4 m·s^(-1)and 1.4 bar(1 bar=105 Pa),respectively,were then applied to drive pilot-scale microfiltration tests to reuse the collected permeate as a new cultivation medium for *** growth in a pilot-scale *** investigation revealed key differences between the behavior of the membrane systems at the two scales(bench and pilot).It indicated the potential for beneficial reuse of the permeate stream as the pilot-scale experiments ensured high harvesting performance and growth rates of biomass in permeate water that were highly similar to those recorded in the ideal cultivation ***,different nutrient reintegration protocols were investigated,revealing that both macro-and micro-nutrient levels are critical for the success of the reuse approach.

关键词： Scenedesmus obliquus Microfiltration Permeate reuse Harvesting Microalgae Pilot-scale

Hybrid pedestrian positioning system using wearable inertial sensors and ultrasonic ranging

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Defence Technology（防务技术） 2024年第3期33卷 327-338页

作者： Lin Qi Yu Liu Chuanshun Gao Tao Feng Yue Yu School of Communication and Information Engineering Chongqing University of Posts and TelecommunicationsChongqing 400065China department of land Surveying and Geo-Informatics The Hong Kong Polytechnic UniversityHong Kong 999077China

Pedestrian positioning system(PPS)using wearable inertial sensors has wide applications towards various emerging fields such as smart healthcare,emergency rescue,soldier positioning,*** performance of traditional PPS is limited by the cumulative error of inertial sensors,complex motion modes of pedestrians,and the low robustness of the multi-sensor collaboration *** paper presents a hybrid pedestrian positioning system using the combination of wearable inertial sensors and ultrasonic ranging(H-PPS).A robust two nodes integration structure is developed to adaptively combine the motion data acquired from the single waist-mounted and foot-mounted node,and enhanced by a novel ellipsoid constraint *** addition,a deep-learning-based walking speed estimator is proposed by considering all the motion features provided by different nodes,which effectively reduces the cumulative error originating from inertial ***,a comprehensive data and model dual-driven model is presented to effectively combine the motion data provided by different sensor nodes and walking speed estimator,and multi-level constraints are extracted to further improve the performance of the overall *** results indicate that the proposed H-PPS significantly improves the performance of the single PPS and outperforms existing algorithms in accuracy index under complex indoor scenarios.

关键词： Pedestrian positioning system Wearable inertial sensors Ultrasonic ranging Deep-learning Data and model dual-driven

Comparative Analysis of Metro Passengers' Mobility Patterns and Jobs-housing Balance of Metropolitan

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Journal of Geodesy and Geoinformation Science 2024年第2期 1-17页

作者： HUANG Yiman ZHANG Anshu SU Yuezhu SHI Wenzhong department of land Surveying and Geo-Informatics The Hong Kong Polytechnic University Otto Poon Charitable Foundation Smart Cities Research Institute and department of and land Surveying and Geo-Informatics The Hong Kong Polytechnic University

The advent of the big data era has provided many types of transportation datasets, such as metro smart card data,for studying residents' mobility and understanding how their mobility has been shaped and is shaping the urban space. In this paper, we use metro smart card data from two Chinese metropolises, Shanghai and Shenzhen. Five metro mobility indicators are introduced, and association rules are established to explore the mobility *** proportion of people entering and exiting the station is used to measure the jobs-housing balance. It is found that the average travel distance and duration of Shanghai passengers are higher than those of Shenzhen,and the proportion of metro commuters in Shanghai is higher than that of Shenzhen. The jobs-housing spatial relationship in Shenzhen based on metro travel is more balanced than that in Shanghai. The fundamental reason for the differences between the two cities is the difference in urban morphology. Compared with the monocentric structure of Shanghai, the polycentric structure of Shenzhen results in more scattered travel hotspots and more diverse travel routes, which helps Shenzhen to have a better jobs-housing balance. This paper fills a gap in comparative research among Chinese cities based on transportation big data analysis. The results provide support for planning metro routes, adjusting urban structure and land use to form a more reasonable metro network, and balancing the jobs-housing spatial relationship.

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Paleoenvironmental changes recorded by grain size of loess/paleosol sequence from the Chifeng City,Northeastern China since the Last Glacial

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Journal of Mountain Science 2024年第9期21卷 3068-3082页

作者： LI Juan BRYE Kristofor R ZHANG Mengge JIANG Zhuodong WANG Qiubing College of land and Environment Shenyang Agricultural UniversityShenyang 110866China department of Crop Soiland Environmental SciencesUniversity of ArkansasFayettevilleAR 72701USA

The accumulation processes of loess in northeastern(NE)China record the varying characteristics of the East Asian Monsoons(EAM)and the evolution of the local *** this study,grain size end-member analysis of the Dajiugang(DJG)section deposited since the Last Glacial in Chifeng City,NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE *** showed that the Chifeng loess comprises three grain size end-members(EM),EM1(7.38μm),EM2(49.4μm)and EM3(90.00μm),indicating the three transport dynamics of dust delivered to the *** EM1 represents atmospheric dust as the *** EM2,mainly derived from relatively distant-sources deposition,and EM3,material transported over a short distance,correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon(EAWM),*** of climate reconstruction,combined with other records,showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon(EASM)during the stadial-period[Marine Isotope Stage(MIS)4 and MIS 2 stage].The climate was predominantly warm and humid,with weak EAWM and surface winds and strong EASM in interstadial-period(MIS 3 and MIS 1 stage).Comparisons between indicators,e.g.,EM3,the LR04 benthicδ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation.

关键词： Loess deposit Grain size end-member Northeastern China Environmental change The Last Glacial

Sliding behaviors of the trapezoidal roof rock block under a lateral dynamic disturbance

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第3期16卷 741-760页

作者： Feng Dai Wancheng Zhu Min Ren Shunchuan Wu Leilei Niu Faculty of land Resources Engineering Kunming University of Science and TechnologyKunming650093China Center for Rock Instability and Seismicity Research Department of Mining EngineeringSchool of Resource and Civil EngineeringNortheastern UniversityShenyang110819China

The surrounding rock of underground space is always affected by external dynamic disturbance from the side position,such as blasting vibration from a stope at the same level or seismic waves from adjacent strata.A series of laboratory tests,numerical simulations and theoretical analyses were carried out in this study to disclose the sliding mechanism of roof rock blocks under lateral ***,the experiments on trapezoidal key block under various clamping loads and disturbance were conducted,followed by numerical simulations using the fast Lagrangian analysis of continua(FLAC3D).Then,based on the conventional wave propagation model and the classical shear-slip constitutive model,a theoretical model was proposed to capture the relative displacement between blocks and the sliding displacement of the key *** results indicate that the sliding displacement of the key block increased linearly with the disturbance energy and decreased exponentially with the clamping load when the key block was disturbed to slide(without instability).Meanwhile,when the key block was disturbed to fall,two types of instability process may appear as immediate type or delayed *** addition,the propagation of stress waves in the block system exhibited obvious low-velocity and lowfrequency characteristics,resulting in the friction reduction effect appearing at the contact interface,which is the essential reason for the sliding of rock *** results can be applied to practical underground engineering and provide valuable guidance for the early detection and prevention of rockfalling disasters.

关键词： Lateral dynamic disturbance Trapezoidal rock block system Low-velocity and low-frequency wave Friction reduction effect Instability mode

Challenges in applying REE-based thermobarometers: Insights from mafic-ultramafic granulites in Indian southern granulite terrain

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Science China Earth Sciences 2024年

作者： Xiaofei XU Longlong GOU Chengli ZHANG Junsheng LU Yan ZHAO Wenhao AO Yuhua HU Feng ZHOU Faculty of land Resources Engineering Kunming University of Science and Technology State Key Laboratory of Continental Dynamics Department of Geology Northwest University

High-temperature diffusion of major elements may obscure the records of early and peak metamorphic stages in granulites,while trace elements are more likely to preserve these records due to their lower diffusion ***,using calibrated REE-based thermobarometers has proved essential for reconstructing these key stages,drawing considerable attention and application from ***,the precision of these thermobarometers depends on including both major and trace elements from coexisting minerals to define the correlation coefficients（A,B,and D） among mineral pairs,indicating that the elemental composition of these pairs can affect the *** study examines the mafic-ultramafic granulites in the southern granulite terrain,India,employing integrated methods such as petrography,mineral chemistry,phase equilibrium modeling,and REE-based *** aim to determine their metamorphic conditions and evolutionary history and to identify potential challenges in using REE-based *** garnet,clinopyroxene,and orthopyroxene in the mafic-ultramafic granulite samples display homogeneous compositional profiles,with pronounced Fe-Mg diffusion zones at the interfaces between garnet and ***,the profiles of trace elements within garnet and clinopyroxene are better *** into Fe-Mg exchange and randomly selected mineral pairs significantly influence the accuracy of REE-based ***-Mg exchange can increase in coefficient A,while decreasing coefficient B for light rare earth elements（LREEs） and increasing it for heavy rare earth elements（HREEs）,ultimately resulting in overestimations when calculating REE-based *** example,selecting major compositions with an Ex(=(XMgC-XMg0)/XMg0×100%;where XMgCis the value after Fe-Mg exchange,XMg0is the value before Fe-Mg exchange;XMg=Mg/(Fe2++Mg)) value of ～10 for calculation using the REE-in-Grt-Cpx thermobarometer will result in pressures and t

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Arbuscular mycorrhizal fungi regulate plant mineral nutrient uptake and partitioning in iron ore tailings undergoing eco-engineered pedogenesis

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Pedosphere 2024年第2期34卷 385-398页

作者： Zhen LI Songlin WU Yunjia LIU Qing YI Merinda HALL Narottam SAHA Junjian WANG Yuanfang HUANG Longbin HUANG College of land Science and Technology China Agricultural UniversityBeijing 100193China Centre for Mined land Rehabilitation Sustainable Minerals InstituteThe University of QueenslandBrisbaneQLD 4072Australia Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control School of Environmental Science and EngineeringSouthern University of Science and TechnologyShenzhen 518055China

Excess available K and Fe in Fe ore tailings with organic matter amendment and water-deficiencies may restrain plant colonization and growth,which hinders the formation of eco-engineered soil from these tailings for sustainable and cost-effective mine site *** mycorrhizal(AM)fungi are widely demonstrated to assist plant growth under various unfavorable ***,it is still unclear whether AM symbiosis in tailings amended with different types of plant biomass and under different water conditions could overcome the surplus K and Fe stress for plants in Fe ore tailings,and if so,by what ***,host plants(Sorghum *** ***),either colonized or noncolonized by the AM fungi(Glomus spp.),were cultivated in lucerne hay(LH,C:N ratio of 18)-or sugarcane mulch(SM,C:N ratio of 78)-amended Fe ore tailings under well-watered(55%water-holding capacity(WHC)of tailings)or water-deficient(30%WHC of tailings)*** mycorrhizal colonization,plant growth,and mineral elemental uptake and partitioning were *** indicated that AM fungal colonization improved plant growth in tailings amended with plant biomass under water-deficient *** mycorrhizal fungal colonization enhanced plant mineral element uptake,especially P,both in the LH-and SM-amended tailings regardless of water ***,AM symbiosis development restrained the translocation of excess elements(i.e.,K and Fe)from plant roots to shoots,thereby relieving their *** AM fungal roles in P uptake and excess elemental partitioning were greater in LH-amended tailings than in SM-amended *** deficiency weakened AM fungal colonization and functions in terms of mineral element uptake and *** findings highlighted the vital role AM fungi played in regulating plant growth and nutrition status in Fe ore tailings technosol,providing an important basis for involvement of AM fungi in the eco-engineered pedo

关键词： Fe stress fungal symbiosis K stress mine site rehabilitation mycorrhizal colonization plant biomass amendment plant nutrition water deficiency