This study explores the use of the Global Navigation Satellite System(GNSS)precise point positioning(PPP)technology to determine the natural vibration periods of towering structures through simulations and field testi...This study explores the use of the Global Navigation Satellite System(GNSS)precise point positioning(PPP)technology to determine the natural vibration periods of towering structures through simulations and field testing.During the simulation phase,a GNSS receiver captured vi-bration waveforms generated by a single-axis motion simulator based on preset signal parameters,analyzing how different satellite system configurations affect the efficiency of extracting vibration parameters.Subsequently,field tests were conducted on a high-rise steel singletube tower.The results indicate that in the simulation environment,no matter the PPP positioning data under single GPS or multisystem combination,the vibration frequency of singleaxis motion simulator can be accurately extracted after frequency do-main analysis,with multisystem setups providing more precise amplitude parameters.In the field test,the natural vibration periods of the main vibration modes of high-rise steel single-tube tower measured by PPP technology closely match the results of the first two modes derived from finite element analysis.The first mode period calculated by the em-pirical formula is approximately 6%higher than those determined through finite element analysis and PPP.This study demonstrates the potential of PPP for structural vibration analysis,offering significant benefits for assessing dynamic responses and monitoring the health of towering structures.展开更多
Rapid urbanization has led to a surge in the number of towering structures,and overturning is widely used because it can better accommodate the construction of shaped structures such as variable sections.The complexit...Rapid urbanization has led to a surge in the number of towering structures,and overturning is widely used because it can better accommodate the construction of shaped structures such as variable sections.The complexity of the construction process makes the construction risk have certain randomness,so this paper proposes a cloudbased coupled matter-element model to address the ambiguity and randomness in the safety risk assessment of overturning construction of towering structures.In the pretended model,the digital eigenvalues of the cloud model are used to replace the eigenvalues in the matter–element basic element,and calculate the cloud correlation of the risk assessment metrics through the correlation algorithm of the cloud model to build the computational model.Meanwhile,the improved hierarchical analysis method based on the cloud model is used to determine the weight of the index.The comprehensive evaluation scores of the evaluation event are then obtained through the weighted average method,and the safety risk level is determined accordingly.Through empirical analysis,(1)the improved hierarchical analysis method based on the cloud model can incorporate the data of multiple decisionmakers into the calculation formula to determine theweights,which makes the assessment resultsmore credible;(2)the evaluation results of the cloud-basedmatter-element coupledmodelmethod are basically consistent with those of the other two commonly used methods,and the confidence factor is less than 0.05,indicating that the cloudbased physical element coupled model method is reasonable and practical for towering structure overturning;(3)the cloud-based coupled element model method,which confirms the reliability of risk level by performing Spearman correlation on comprehensive assessment scores,can provide more comprehensive information of instances compared with other methods,and more comprehensively reflects the fuzzy uncertainty relationship between assessment indexes,which makes the assessment results more realistic,scientific and reliable.展开更多
Over a century and half has passed when Bernhard Riemann hypothesized that the non-trivial roots of the Riemann zeta function ζ(s) all lie on the half-line . In this paper the Zeta function is iterated as a power tow...Over a century and half has passed when Bernhard Riemann hypothesized that the non-trivial roots of the Riemann zeta function ζ(s) all lie on the half-line . In this paper the Zeta function is iterated as a power tower and its properties are applied as an approach to an indication that the Riemann hypothesis might be true. It is known that complex valued Power towers converge under certain conditions to exponential power towers of entire functions. These properties can be used to resolve the Riemann Hypothesis.展开更多
As China’s first desert natural heritage site,Badain Jaran Desert captivates the human imagination not only with its sand,but water,life and culture,says archeologist Ge Zhiyong.On July 26,2024,China’s Badain Jaran ...As China’s first desert natural heritage site,Badain Jaran Desert captivates the human imagination not only with its sand,but water,life and culture,says archeologist Ge Zhiyong.On July 26,2024,China’s Badain Jaran Desert-Towers of Sand and Lakes,was inscribed as a UNESCO World Heritage site by the United Nations Educational,Scientific and Cultural Organization during the 46th session of the World Heritage Committee in New Delhi,India.It is the first world natural heritage site in China’s Inner Mongolia Autonomous Region and the country’s first desert natural heritage site.展开更多
Over the past months,a southern Chinese harbor serving as a pivotal gateway to regions around the world has come into the spotlight after the launching of special customs operations on Hainan Island.LOCATED on the nor...Over the past months,a southern Chinese harbor serving as a pivotal gateway to regions around the world has come into the spotlight after the launching of special customs operations on Hainan Island.LOCATED on the northwest tip of HainanIsland,the Yangpu Port is a scene ofbustling activity with towering gantrycranes busily loading containers on andoff large cargo vessels.Port orders here have surgedas a result of a slew of special customs policiesthat went into force last December.展开更多
The advancement of integrated die-casting technology calls for high-strength,high-ductility heat-treatment-free Al alloys.This study investigates the use of a new AlSiFeMnVTiSrZr heat-treatment-free die-casting alloy ...The advancement of integrated die-casting technology calls for high-strength,high-ductility heat-treatment-free Al alloys.This study investigates the use of a new AlSiFeMnVTiSrZr heat-treatment-free die-casting alloy for shock tower manufacturing.Results show the alloy has excellent overall mechanical properties,but significant regional differences in microstructure and performance are found in the shock tower casting:Far-gate Position 6 has almost no externally solidified crystals(ESCs),whereas dense coarse dendritic ESCs exist in the center of near-gate Position 5.The fracture surface of Position 6 shows a steeper slope,while Position 5 has a rough crack propagation platform.Far-gate Position 6 also has higher porosity(nearly triple that of near-gate Region 5)and larger average pore size.Analysis reveals microstructural heterogeneity between near-and far-gate regions strongly influences mechanical performance.Notably,coarse dendritic ESCs in the near-gate region restrict grain boundary strengthening,leading to lower yield strength despite low porosity.Conversely,while fine grains in the far-gate region could enhance grain boundary strengthening,abundant porosity acts as crack initiation sites,severely reducing ductility.These findings provide theoretical guidance for evaluating integrated die-cast component performance.展开更多
If you're tired of megacities that feel like nothing but glass,steel,and constant rush,Guangzhou moves at its own pace.Here,a 19th-century ancestral hall stands next to a 600-meter tower,and the day begins with te...If you're tired of megacities that feel like nothing but glass,steel,and constant rush,Guangzhou moves at its own pace.Here,a 19th-century ancestral hall stands next to a 600-meter tower,and the day begins with tea and delicate steamed treats instead of coffee.展开更多
Heliostat field design for tower solar thermal plants must jointly address solar geometry,optical losses,and layout optimization under engineering constraints.We develop an end-to-end workflow that(i)adopts a consiste...Heliostat field design for tower solar thermal plants must jointly address solar geometry,optical losses,and layout optimization under engineering constraints.We develop an end-to-end workflow that(i)adopts a consistent East–North–Up(ENU)convention for all plant-and sun-related vectors;(ii)integrates cosine efficiency,projection-based shading and blocking(SB),atmospheric transmittance,and an HFLCAL(heliostat field local calculation)truncation model into a single optical chain;and(iii)couples an Eliminate-Blocking(EB)layout prior with an improved“Cheetah”metaheuristic to search ring topology,mirror sizes,and heights while enforcing spacing,kinematics,and rated-power requirements.Projection-based SB is calibrated against Monte-Carlo ray tracing at representative sun positions,and the HFLCAL truncation model is used to quantify sensitivities to sunshape and error-budget parameters.In a three-phase study(fixed-size baseline,uniform sizing,heterogeneous sizing),the EB-guided optimizer improves annual per-area output relative to a radial baseline and reliably attains a 60 MW target.Under equal evaluation budgets,the proposed optimizer converges faster and with lower variance than GA-and PSO-based baselines,while respecting panel-level peak-flux limits through a smooth penalization of flux violations.The resulting layouts exhibit outward-increasing azimuthal spacing and ring-wise size sharing that are consistent with recent heliostat-field deployment experience.The framework is modular,auditable,and readily adaptable to alternative receivers,sites,and cost-aware objectives.展开更多
This study aims to mitigate crosswind-induced performance degradation in Natural Draft Dry Cooling Towers used in power plants by developing and assessing windbreak configurations that enhance ventilation while minimi...This study aims to mitigate crosswind-induced performance degradation in Natural Draft Dry Cooling Towers used in power plants by developing and assessing windbreak configurations that enhance ventilation while minimizing additional airflow resistance.Three novel windbreak designs,namely single-windbreak configuration with curved profile,double-windbreak configuration with curved profile,and double-windbreak configuration with inverted curved profile,are proposed accordingly and evaluated against conventional solutions.Three-dimensional numerical models of a 120 m high NDDCT equipped with these windbreaks,together with a conventional Y-shaped windbreak,are developed for systematic comparison.The results demonstrate that windbreak effectiveness strongly depends on crosswind intensity.At low crosswind speeds of 0-6 m/s,the Y-shaped windbreak provides the greatest enhancement,increasing the ventilation rate by 25.45%and the heat rejection rate by 21.37%at 6 m/s compared with the no-windbreak configuration.In contrast,under moderate to strong crosswinds of 6-18 m/s,the single-windbreak configuration with curved profile exhibits superior performance.At 18 m/s,it increases the ventilation rate by 148.88%and the heat rejection rate by 79.74%relative to the baseline case,outperforming the Y-shaped windbreak by 26.59%in ventilation rate and 17.01%in heat rejection capacity.Analysis of airflow structure,temperature fields,and velocity distributions confirms that the single-windbreak configuration with curved profile more effectively suppresses crosswind penetration and promotes stable upward airflow at higher wind speeds.Based on a comprehensive assessment of aerodynamic and thermal performance,the Y-shaped windbreak is recommended for regions where crosswind speeds remain below 6 m/s,whereas the single-windbreak configuration with curved profile is preferable for sites exposed to stronger crosswinds exceeding this threshold.展开更多
The virtual preassembly of super-high steel bridge towers faces a challenge in the efficient and precise extraction of complex cross-sectional features.Factors such as fabrication errors,gravity-induced deformations,a...The virtual preassembly of super-high steel bridge towers faces a challenge in the efficient and precise extraction of complex cross-sectional features.Factors such as fabrication errors,gravity-induced deformations,and temperature fluctuations can compromise the accuracy of contour extraction.To address these limitations,an improved Alpha-shape-based point cloud contour extraction method is proposed.The proposed approach uses a hierarchical strategy to process three-dimensional laser scanning point clouds.The processed data are then subjected to curvatureadaptive voxel filtering to reduce acquisition noise.In addition,an enhanced iterative closest point(ICP)variant with correspondence validation accurately aligns the discrete point cloud segments.The proposed curvature-responsive Alpha-shape framework enables multiscale contour delineation through topology-adaptive threshold modulation,which resolves boundary ambiguities in geometrically complex cross-sections.The method was experimentally validated using field-acquired measurement datasets from the Zhangjinggao Yangtze River Bridge tower segments,confirming its capability to reconstruct noncanonical cross-sectional geometries.Three contour extraction methods,including Poisson reconstruction,the conventional Alpha-shape algorithm,and random sample consensus with ICP(RANSAC-ICP),were compared to evaluate the performance of the proposed Alpha-shape algorithm.The results demonstrate that the proposed method achieves superior contour extraction accuracy and data reduction efficiency,highlighting its effectiveness in contour extraction tasks.展开更多
Lattice-type ultra-tall wind turbine towers are popular in China for their modular benefits in fabrication,transportation,and installation.Nonetheless,their conceptual design remains predominantly dependent on enginee...Lattice-type ultra-tall wind turbine towers are popular in China for their modular benefits in fabrication,transportation,and installation.Nonetheless,their conceptual design remains predominantly dependent on engineering experience,and a generally applicable approach is still absent.This study proposes a self-similar modular topology optimization framework for lattice-type wind turbine support structures and develops software for its application.A minimum weighted compliance formulation with a prescribed volume fraction is developed utilizing the variable density approach,wherein modular constraints and their corresponding sensitivity expressions are explicitly included.The method is applied to a reference wind turbine model to generate modular lattice configurations.The novel structural models are evaluated under three representative design load cases outlined in IEC 61400 by finite element analysis.Compared with the reference structure,the 12-layer self-similar modular design reduces the maximum deformation and von Mises stress by 39.5%and 51.1%,respectively,demonstrating a substantial stiffness improvement while preserving modularity.The suggested approach provides an efficient and practical tool for the conceptual design of modular lattice-type wind turbine towers.展开更多
The South Central Axis in Beijing showcases China’s image and highlights its cultural confidence.THE Central Axis is the centerpiece of the Chinese capital’s urban spatial layout.The southern extended section of the...The South Central Axis in Beijing showcases China’s image and highlights its cultural confidence.THE Central Axis is the centerpiece of the Chinese capital’s urban spatial layout.The southern extended section of the Central Axis,or the South Central Axis,stretches from the Yongdingmen Gate Tower in the north to the South Fifth Ring Road in the south.While being a strategic transport link facilitating the coordinated development of the Beijing-Tianjin-Hebei region,it also showcases China’s vision for the future and highlights its cultural confidence.展开更多
To investigate the impact of temporary structures on the mechanical behavior of shaped bridge towers during the construction process,the Dianbu River Special Bridge was selected as the engineering background.A finite ...To investigate the impact of temporary structures on the mechanical behavior of shaped bridge towers during the construction process,the Dianbu River Special Bridge was selected as the engineering background.A finite element model of the middle tower column during the construction stage was established using ABAQUS to analyze the effects of key parameters,including the angle and pretension of temporary cables,as well as the wall thickness and diameter of temporary diagonal braces.The study examines how these parameters influence the stresses at the towergirder consolidation.The results indicate that the angle of temporary cables significantly affects the tensile stresses at the tower-girder consolidation,while its impact on compressive stresses is minimal.Among all parameters,the pretension of temporary cables has the most pronounced effect on the stresses at the tower-girder consolidation.In contrast,the wall thickness of temporary diagonal braces has only a minor influence,whereas the diameter of temporary diagonal braces has an almost negligible impact.These findings provide valuable insights for optimizing the design and arrangement of temporary support structures in similar bridge construction projects.展开更多
Withstanding the tough test of SARS in 2003,Beijing Plaza Hotel is steering itself on to a path of business.Well positioned,the ambitious hotel is becoming a vanguard player in the industry.Beijing Review conducted an...Withstanding the tough test of SARS in 2003,Beijing Plaza Hotel is steering itself on to a path of business.Well positioned,the ambitious hotel is becoming a vanguard player in the industry.Beijing Review conducted an exclusive interview with Miss.Liu Jingying,Sales Director of the hotel展开更多
世界第一树王最近已经易主。原世界树王名称是Tall Tree,是一棵美国红杉树,高112.18米,不料,一场冬季的风暴折断了它顶部,骤然使它“矮”了3米。现在,取而代之的是另一棵美国红杉树,其高度为112.08米,被命名为theMendocino Tree,其树龄...世界第一树王最近已经易主。原世界树王名称是Tall Tree,是一棵美国红杉树,高112.18米,不料,一场冬季的风暴折断了它顶部,骤然使它“矮”了3米。现在,取而代之的是另一棵美国红杉树,其高度为112.08米,被命名为theMendocino Tree,其树龄估计在600年到800年之间,地点在美国加州北部的Ukiah西部19公里处的密林中。这一事实已经得到了官方的确认,并收入了Guinness Book of World Records(吉尼斯世界记录大全)。这篇报道除了有关“树王”的信息外,还附带了不少有趣的事实。如,当地居民并不以此为荣,或大肆宣扬,甚至把它当作一棵“摇钱树”,相反,为了保护新“树王”,他们断然采取了措施: …some local residents were actually taking down signs to discouragevisitors. 此句中的动词discourage用得真好,值得我们多视角地去咀嚼玩味。】展开更多
The Yarlung Zangbo Grand Canyon,located in Xizang,China,is known as the deepest canyon on Earth.With a maximum depth of over 6,000 meters—over three times the depth of the Grand Canyon in the United States—it stretc...The Yarlung Zangbo Grand Canyon,located in Xizang,China,is known as the deepest canyon on Earth.With a maximum depth of over 6,000 meters—over three times the depth of the Grand Canyon in the United States—it stretches for more than 500 kilometers through the Himalayan Mountains.This natural wonder was formed by the powerful erosion(侵蚀)of the Yarlung Zangbo River over millions of years,as the river cut deeper and deeper into the earth's crust,creating a landscape of towering peaks and narrow canyons.展开更多
The fuzzy comfortability of a wind-sensitive super-high tower crane is critical to guarantee occupant health and improve construction efficiency.Therefore,the wind-resistant fuzzy comfortability of a super-high tower ...The fuzzy comfortability of a wind-sensitive super-high tower crane is critical to guarantee occupant health and improve construction efficiency.Therefore,the wind-resistant fuzzy comfortability of a super-high tower crane in the Ma’anshan Yangtze River(MYR)Bridge site is analyzed in this paper.First,the membership function model that represents fuzzy comfortability is introduced in the probability density evolution method(PDEM).Second,based on Fechner’s law,the membership function curves are constructed according to three acceleration thresholds in ISO 2631.Then,the fuzzy comfortability for the super-high tower crane under stochastic wind loads is assessed on the basis of different cut-set levelsλ.Results show that the comfortability is over 0.9 under the required maximum operating wind velocity.The low sensitivity toλcan be observed in the reliability curves of ISOⅡandⅢmembership functions.The reliability of the ISOⅠmembership function is not sensitive toλwhenλ<0.7,whereas it becomes sensitive toλwhenλ>0.7.展开更多
The efficient implementation of the Advanced Encryption Standard(AES)is crucial for network data security.This paper presents novel hardware implementations of the AES S-box,a core component,using tower field represen...The efficient implementation of the Advanced Encryption Standard(AES)is crucial for network data security.This paper presents novel hardware implementations of the AES S-box,a core component,using tower field representations and Boolean Satisfiability(SAT)solvers.Our research makes several significant contri-butions to the field.Firstly,we have optimized the GF(24)inversion,achieving a remarkable 31.35%area reduction(15.33 GE)compared to the best known implementations.Secondly,we have enhanced multiplication implementa-tions for transformation matrices using a SAT-method based on local solutions.This approach has yielded notable improvements,such as a 22.22%reduction in area(42.00 GE)for the top transformation matrix in GF((24)2)-type S-box implementation.Furthermore,we have proposed new implementations of GF(((22)2)2)-type and GF((24)2)-type S-boxes,with the GF(((22)2)2)-type demonstrating superior performance.This implementation offers two variants:a small area variant that sets new area records,and a fast variant that establishes new benchmarks in Area-Execution-Time(AET)and energy consumption.Our approach significantly improves upon existing S-box implementations,offering advancements in area,speed,and energy consumption.These optimizations contribute to more efficient and secure AES implementations,potentially enhancing various cryptographic applications in the field of network security.展开更多
Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect ...Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect the safety and stability of transmission towers.In this study,the effects of bolt joint loosening on the dynamic characteristics of a 220-kV angle steel transmission tower are the main topic of concern.First,the mechanical properties of typical joints subjected to different degrees of bolt loosening are studied by finite solid-element simulation,based on which a finite hybrid-element modeling method is developed for a tower structure suffering varying loose degrees in the joints.Taking a 220-kV angle steel transmission tower as the object,the influence of the position and degree of loosening on the tower’s natural frequencies and mode shapes are simulated and discussed.The results demonstrate that the main-member splice joint and the main diagonal-horizontal member gusset plate joint account for the dominant impact on the dynamic characteristics of the tower.In addition,the dominant joint shifts from the main-member splice joint to the main diagonal-horizontal member gusset plate joint as the considered modal order increases.In the case of double joints loosening simultaneously,the loosening of nondomi-nant joints has nonnegligible effects on the tower as well.展开更多
The Beijing 325 m meteorological tower stands as a pivotal research platform for exploring atmospheric boundary layer physics and atmospheric chemistry.With a legacy spanning 45 years,the tower has played a crucial ro...The Beijing 325 m meteorological tower stands as a pivotal research platform for exploring atmospheric boundary layer physics and atmospheric chemistry.With a legacy spanning 45 years,the tower has played a crucial role in unraveling the complexities of urban air pollution,atmospheric processes,and climate change in Beijing,China.This review paper provides a comprehensive overview of the measurements on the tower over the past two decades.Through long-term comprehensive observations,researchers have elucidated the intricate relationships between anthropogenic emissions,meteorological dynamics,and atmospheric composition,shedding light on the drivers of air pollution and its impacts on public health.The vertical measurements on the tower also enable detailed investigations into boundary layer dynamics,turbulent mixing,and pollutant dispersion,providing invaluable data for validating chemical transport models.Key findings from the tower’s research include the identification of positive feedback mechanisms between aerosols and the boundary layer,the characterization of pollutant sources and transport pathways,the determination of fluxes of gaseous and particulate species,and the assessment of the effectiveness of pollution control measures.Additionally,isotopic measurements have provided new insights into the sources and formation processes of particulate matter and reactive nitrogen species.Finally,the paper outlines future directions for tower-based research,emphasizing the need for long-term comprehensive measurements,the development of innovative tower platforms,and integration of emerging technologies.展开更多
基金The National Natural Science Foundation of China(No.41974214).
文摘This study explores the use of the Global Navigation Satellite System(GNSS)precise point positioning(PPP)technology to determine the natural vibration periods of towering structures through simulations and field testing.During the simulation phase,a GNSS receiver captured vi-bration waveforms generated by a single-axis motion simulator based on preset signal parameters,analyzing how different satellite system configurations affect the efficiency of extracting vibration parameters.Subsequently,field tests were conducted on a high-rise steel singletube tower.The results indicate that in the simulation environment,no matter the PPP positioning data under single GPS or multisystem combination,the vibration frequency of singleaxis motion simulator can be accurately extracted after frequency do-main analysis,with multisystem setups providing more precise amplitude parameters.In the field test,the natural vibration periods of the main vibration modes of high-rise steel single-tube tower measured by PPP technology closely match the results of the first two modes derived from finite element analysis.The first mode period calculated by the em-pirical formula is approximately 6%higher than those determined through finite element analysis and PPP.This study demonstrates the potential of PPP for structural vibration analysis,offering significant benefits for assessing dynamic responses and monitoring the health of towering structures.
基金funded by China Railway No.21 Bureau Group No.1 Engineering Co.,Ltd.,Grant No.202209140002.
文摘Rapid urbanization has led to a surge in the number of towering structures,and overturning is widely used because it can better accommodate the construction of shaped structures such as variable sections.The complexity of the construction process makes the construction risk have certain randomness,so this paper proposes a cloudbased coupled matter-element model to address the ambiguity and randomness in the safety risk assessment of overturning construction of towering structures.In the pretended model,the digital eigenvalues of the cloud model are used to replace the eigenvalues in the matter–element basic element,and calculate the cloud correlation of the risk assessment metrics through the correlation algorithm of the cloud model to build the computational model.Meanwhile,the improved hierarchical analysis method based on the cloud model is used to determine the weight of the index.The comprehensive evaluation scores of the evaluation event are then obtained through the weighted average method,and the safety risk level is determined accordingly.Through empirical analysis,(1)the improved hierarchical analysis method based on the cloud model can incorporate the data of multiple decisionmakers into the calculation formula to determine theweights,which makes the assessment resultsmore credible;(2)the evaluation results of the cloud-basedmatter-element coupledmodelmethod are basically consistent with those of the other two commonly used methods,and the confidence factor is less than 0.05,indicating that the cloudbased physical element coupled model method is reasonable and practical for towering structure overturning;(3)the cloud-based coupled element model method,which confirms the reliability of risk level by performing Spearman correlation on comprehensive assessment scores,can provide more comprehensive information of instances compared with other methods,and more comprehensively reflects the fuzzy uncertainty relationship between assessment indexes,which makes the assessment results more realistic,scientific and reliable.
文摘Over a century and half has passed when Bernhard Riemann hypothesized that the non-trivial roots of the Riemann zeta function ζ(s) all lie on the half-line . In this paper the Zeta function is iterated as a power tower and its properties are applied as an approach to an indication that the Riemann hypothesis might be true. It is known that complex valued Power towers converge under certain conditions to exponential power towers of entire functions. These properties can be used to resolve the Riemann Hypothesis.
文摘As China’s first desert natural heritage site,Badain Jaran Desert captivates the human imagination not only with its sand,but water,life and culture,says archeologist Ge Zhiyong.On July 26,2024,China’s Badain Jaran Desert-Towers of Sand and Lakes,was inscribed as a UNESCO World Heritage site by the United Nations Educational,Scientific and Cultural Organization during the 46th session of the World Heritage Committee in New Delhi,India.It is the first world natural heritage site in China’s Inner Mongolia Autonomous Region and the country’s first desert natural heritage site.
文摘Over the past months,a southern Chinese harbor serving as a pivotal gateway to regions around the world has come into the spotlight after the launching of special customs operations on Hainan Island.LOCATED on the northwest tip of HainanIsland,the Yangpu Port is a scene ofbustling activity with towering gantrycranes busily loading containers on andoff large cargo vessels.Port orders here have surgedas a result of a slew of special customs policiesthat went into force last December.
基金the National Natural Science Foundation of China(Grant Nos.52405342 and 52175335)the National Key Research and Development Program of China(Grant No.2022YFB3404201)+2 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.N2302014 and N25ZJL003)the Natural Science Foundation Joint Foundation of Liaoning province(Grant No.2023-BSBA-108)the help provided by China FAW Foundry Co.,Ltd.
文摘The advancement of integrated die-casting technology calls for high-strength,high-ductility heat-treatment-free Al alloys.This study investigates the use of a new AlSiFeMnVTiSrZr heat-treatment-free die-casting alloy for shock tower manufacturing.Results show the alloy has excellent overall mechanical properties,but significant regional differences in microstructure and performance are found in the shock tower casting:Far-gate Position 6 has almost no externally solidified crystals(ESCs),whereas dense coarse dendritic ESCs exist in the center of near-gate Position 5.The fracture surface of Position 6 shows a steeper slope,while Position 5 has a rough crack propagation platform.Far-gate Position 6 also has higher porosity(nearly triple that of near-gate Region 5)and larger average pore size.Analysis reveals microstructural heterogeneity between near-and far-gate regions strongly influences mechanical performance.Notably,coarse dendritic ESCs in the near-gate region restrict grain boundary strengthening,leading to lower yield strength despite low porosity.Conversely,while fine grains in the far-gate region could enhance grain boundary strengthening,abundant porosity acts as crack initiation sites,severely reducing ductility.These findings provide theoretical guidance for evaluating integrated die-cast component performance.
文摘If you're tired of megacities that feel like nothing but glass,steel,and constant rush,Guangzhou moves at its own pace.Here,a 19th-century ancestral hall stands next to a 600-meter tower,and the day begins with tea and delicate steamed treats instead of coffee.
文摘Heliostat field design for tower solar thermal plants must jointly address solar geometry,optical losses,and layout optimization under engineering constraints.We develop an end-to-end workflow that(i)adopts a consistent East–North–Up(ENU)convention for all plant-and sun-related vectors;(ii)integrates cosine efficiency,projection-based shading and blocking(SB),atmospheric transmittance,and an HFLCAL(heliostat field local calculation)truncation model into a single optical chain;and(iii)couples an Eliminate-Blocking(EB)layout prior with an improved“Cheetah”metaheuristic to search ring topology,mirror sizes,and heights while enforcing spacing,kinematics,and rated-power requirements.Projection-based SB is calibrated against Monte-Carlo ray tracing at representative sun positions,and the HFLCAL truncation model is used to quantify sensitivities to sunshape and error-budget parameters.In a three-phase study(fixed-size baseline,uniform sizing,heterogeneous sizing),the EB-guided optimizer improves annual per-area output relative to a radial baseline and reliably attains a 60 MW target.Under equal evaluation budgets,the proposed optimizer converges faster and with lower variance than GA-and PSO-based baselines,while respecting panel-level peak-flux limits through a smooth penalization of flux violations.The resulting layouts exhibit outward-increasing azimuthal spacing and ring-wise size sharing that are consistent with recent heliostat-field deployment experience.The framework is modular,auditable,and readily adaptable to alternative receivers,sites,and cost-aware objectives.
基金supported by the National Natural Science Foundation of China(Grant No.52476206)the Key R&D Program of Shandong Province,China(Grant No.2025CXGC010203)+1 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2025A1515012123)the Shandong Natural Science Foundation(Grant No.ZR2022ME008).
文摘This study aims to mitigate crosswind-induced performance degradation in Natural Draft Dry Cooling Towers used in power plants by developing and assessing windbreak configurations that enhance ventilation while minimizing additional airflow resistance.Three novel windbreak designs,namely single-windbreak configuration with curved profile,double-windbreak configuration with curved profile,and double-windbreak configuration with inverted curved profile,are proposed accordingly and evaluated against conventional solutions.Three-dimensional numerical models of a 120 m high NDDCT equipped with these windbreaks,together with a conventional Y-shaped windbreak,are developed for systematic comparison.The results demonstrate that windbreak effectiveness strongly depends on crosswind intensity.At low crosswind speeds of 0-6 m/s,the Y-shaped windbreak provides the greatest enhancement,increasing the ventilation rate by 25.45%and the heat rejection rate by 21.37%at 6 m/s compared with the no-windbreak configuration.In contrast,under moderate to strong crosswinds of 6-18 m/s,the single-windbreak configuration with curved profile exhibits superior performance.At 18 m/s,it increases the ventilation rate by 148.88%and the heat rejection rate by 79.74%relative to the baseline case,outperforming the Y-shaped windbreak by 26.59%in ventilation rate and 17.01%in heat rejection capacity.Analysis of airflow structure,temperature fields,and velocity distributions confirms that the single-windbreak configuration with curved profile more effectively suppresses crosswind penetration and promotes stable upward airflow at higher wind speeds.Based on a comprehensive assessment of aerodynamic and thermal performance,the Y-shaped windbreak is recommended for regions where crosswind speeds remain below 6 m/s,whereas the single-windbreak configuration with curved profile is preferable for sites exposed to stronger crosswinds exceeding this threshold.
基金The National Natural Science Foundation of China(No.52338011)the Start-up Research Fund of Southeast University(No.RF1028624058)+1 种基金the Southeast University Interdisciplinary Research Program for Young Scholarsthe National Key Research and Development Program of China(No.2024YFC3014103).
文摘The virtual preassembly of super-high steel bridge towers faces a challenge in the efficient and precise extraction of complex cross-sectional features.Factors such as fabrication errors,gravity-induced deformations,and temperature fluctuations can compromise the accuracy of contour extraction.To address these limitations,an improved Alpha-shape-based point cloud contour extraction method is proposed.The proposed approach uses a hierarchical strategy to process three-dimensional laser scanning point clouds.The processed data are then subjected to curvatureadaptive voxel filtering to reduce acquisition noise.In addition,an enhanced iterative closest point(ICP)variant with correspondence validation accurately aligns the discrete point cloud segments.The proposed curvature-responsive Alpha-shape framework enables multiscale contour delineation through topology-adaptive threshold modulation,which resolves boundary ambiguities in geometrically complex cross-sections.The method was experimentally validated using field-acquired measurement datasets from the Zhangjinggao Yangtze River Bridge tower segments,confirming its capability to reconstruct noncanonical cross-sectional geometries.Three contour extraction methods,including Poisson reconstruction,the conventional Alpha-shape algorithm,and random sample consensus with ICP(RANSAC-ICP),were compared to evaluate the performance of the proposed Alpha-shape algorithm.The results demonstrate that the proposed method achieves superior contour extraction accuracy and data reduction efficiency,highlighting its effectiveness in contour extraction tasks.
基金funded by the National Key Research and Development Program of China(No.2024YFE0208600)the National Natural Science Foundation of China(No.U24B2090).
文摘Lattice-type ultra-tall wind turbine towers are popular in China for their modular benefits in fabrication,transportation,and installation.Nonetheless,their conceptual design remains predominantly dependent on engineering experience,and a generally applicable approach is still absent.This study proposes a self-similar modular topology optimization framework for lattice-type wind turbine support structures and develops software for its application.A minimum weighted compliance formulation with a prescribed volume fraction is developed utilizing the variable density approach,wherein modular constraints and their corresponding sensitivity expressions are explicitly included.The method is applied to a reference wind turbine model to generate modular lattice configurations.The novel structural models are evaluated under three representative design load cases outlined in IEC 61400 by finite element analysis.Compared with the reference structure,the 12-layer self-similar modular design reduces the maximum deformation and von Mises stress by 39.5%and 51.1%,respectively,demonstrating a substantial stiffness improvement while preserving modularity.The suggested approach provides an efficient and practical tool for the conceptual design of modular lattice-type wind turbine towers.
文摘The South Central Axis in Beijing showcases China’s image and highlights its cultural confidence.THE Central Axis is the centerpiece of the Chinese capital’s urban spatial layout.The southern extended section of the Central Axis,or the South Central Axis,stretches from the Yongdingmen Gate Tower in the north to the South Fifth Ring Road in the south.While being a strategic transport link facilitating the coordinated development of the Beijing-Tianjin-Hebei region,it also showcases China’s vision for the future and highlights its cultural confidence.
文摘To investigate the impact of temporary structures on the mechanical behavior of shaped bridge towers during the construction process,the Dianbu River Special Bridge was selected as the engineering background.A finite element model of the middle tower column during the construction stage was established using ABAQUS to analyze the effects of key parameters,including the angle and pretension of temporary cables,as well as the wall thickness and diameter of temporary diagonal braces.The study examines how these parameters influence the stresses at the towergirder consolidation.The results indicate that the angle of temporary cables significantly affects the tensile stresses at the tower-girder consolidation,while its impact on compressive stresses is minimal.Among all parameters,the pretension of temporary cables has the most pronounced effect on the stresses at the tower-girder consolidation.In contrast,the wall thickness of temporary diagonal braces has only a minor influence,whereas the diameter of temporary diagonal braces has an almost negligible impact.These findings provide valuable insights for optimizing the design and arrangement of temporary support structures in similar bridge construction projects.
文摘Withstanding the tough test of SARS in 2003,Beijing Plaza Hotel is steering itself on to a path of business.Well positioned,the ambitious hotel is becoming a vanguard player in the industry.Beijing Review conducted an exclusive interview with Miss.Liu Jingying,Sales Director of the hotel
文摘世界第一树王最近已经易主。原世界树王名称是Tall Tree,是一棵美国红杉树,高112.18米,不料,一场冬季的风暴折断了它顶部,骤然使它“矮”了3米。现在,取而代之的是另一棵美国红杉树,其高度为112.08米,被命名为theMendocino Tree,其树龄估计在600年到800年之间,地点在美国加州北部的Ukiah西部19公里处的密林中。这一事实已经得到了官方的确认,并收入了Guinness Book of World Records(吉尼斯世界记录大全)。这篇报道除了有关“树王”的信息外,还附带了不少有趣的事实。如,当地居民并不以此为荣,或大肆宣扬,甚至把它当作一棵“摇钱树”,相反,为了保护新“树王”,他们断然采取了措施: …some local residents were actually taking down signs to discouragevisitors. 此句中的动词discourage用得真好,值得我们多视角地去咀嚼玩味。】
文摘The Yarlung Zangbo Grand Canyon,located in Xizang,China,is known as the deepest canyon on Earth.With a maximum depth of over 6,000 meters—over three times the depth of the Grand Canyon in the United States—it stretches for more than 500 kilometers through the Himalayan Mountains.This natural wonder was formed by the powerful erosion(侵蚀)of the Yarlung Zangbo River over millions of years,as the river cut deeper and deeper into the earth's crust,creating a landscape of towering peaks and narrow canyons.
基金The National Natural Science Foundation of China(No.52108274,52208481,52338011)State Scholarship Fund of China Scholarship Council(No.202306090285).
文摘The fuzzy comfortability of a wind-sensitive super-high tower crane is critical to guarantee occupant health and improve construction efficiency.Therefore,the wind-resistant fuzzy comfortability of a super-high tower crane in the Ma’anshan Yangtze River(MYR)Bridge site is analyzed in this paper.First,the membership function model that represents fuzzy comfortability is introduced in the probability density evolution method(PDEM).Second,based on Fechner’s law,the membership function curves are constructed according to three acceleration thresholds in ISO 2631.Then,the fuzzy comfortability for the super-high tower crane under stochastic wind loads is assessed on the basis of different cut-set levelsλ.Results show that the comfortability is over 0.9 under the required maximum operating wind velocity.The low sensitivity toλcan be observed in the reliability curves of ISOⅡandⅢmembership functions.The reliability of the ISOⅠmembership function is not sensitive toλwhenλ<0.7,whereas it becomes sensitive toλwhenλ>0.7.
基金supported in part by the National Natural Science Foundation of China(No.62162016)in part by the Innovation Project of Guangxi Graduate Education(Nos.YCBZ2023132 and YCSW2023304).
文摘The efficient implementation of the Advanced Encryption Standard(AES)is crucial for network data security.This paper presents novel hardware implementations of the AES S-box,a core component,using tower field representations and Boolean Satisfiability(SAT)solvers.Our research makes several significant contri-butions to the field.Firstly,we have optimized the GF(24)inversion,achieving a remarkable 31.35%area reduction(15.33 GE)compared to the best known implementations.Secondly,we have enhanced multiplication implementa-tions for transformation matrices using a SAT-method based on local solutions.This approach has yielded notable improvements,such as a 22.22%reduction in area(42.00 GE)for the top transformation matrix in GF((24)2)-type S-box implementation.Furthermore,we have proposed new implementations of GF(((22)2)2)-type and GF((24)2)-type S-boxes,with the GF(((22)2)2)-type demonstrating superior performance.This implementation offers two variants:a small area variant that sets new area records,and a fast variant that establishes new benchmarks in Area-Execution-Time(AET)and energy consumption.Our approach significantly improves upon existing S-box implementations,offering advancements in area,speed,and energy consumption.These optimizations contribute to more efficient and secure AES implementations,potentially enhancing various cryptographic applications in the field of network security.
基金The Youth Foundation Project of Jiangsu Province(No.BK20230337)the Natural Science Research of Jiangsu Higher Education Institutions of China(No.22KJB560004)the National Natu-ral Science Foundation of China(No.52278523)。
文摘Transmission towers,serving as the support structure of transmission lines,are significant for the functional-ity of an electric transmission system.Bolt joint loosening is one of the critical factors that can affect the safety and stability of transmission towers.In this study,the effects of bolt joint loosening on the dynamic characteristics of a 220-kV angle steel transmission tower are the main topic of concern.First,the mechanical properties of typical joints subjected to different degrees of bolt loosening are studied by finite solid-element simulation,based on which a finite hybrid-element modeling method is developed for a tower structure suffering varying loose degrees in the joints.Taking a 220-kV angle steel transmission tower as the object,the influence of the position and degree of loosening on the tower’s natural frequencies and mode shapes are simulated and discussed.The results demonstrate that the main-member splice joint and the main diagonal-horizontal member gusset plate joint account for the dominant impact on the dynamic characteristics of the tower.In addition,the dominant joint shifts from the main-member splice joint to the main diagonal-horizontal member gusset plate joint as the considered modal order increases.In the case of double joints loosening simultaneously,the loosening of nondomi-nant joints has nonnegligible effects on the tower as well.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0760200)the National Natural Science Foundation of China(Grant Nos.42330605 and 42377101).
文摘The Beijing 325 m meteorological tower stands as a pivotal research platform for exploring atmospheric boundary layer physics and atmospheric chemistry.With a legacy spanning 45 years,the tower has played a crucial role in unraveling the complexities of urban air pollution,atmospheric processes,and climate change in Beijing,China.This review paper provides a comprehensive overview of the measurements on the tower over the past two decades.Through long-term comprehensive observations,researchers have elucidated the intricate relationships between anthropogenic emissions,meteorological dynamics,and atmospheric composition,shedding light on the drivers of air pollution and its impacts on public health.The vertical measurements on the tower also enable detailed investigations into boundary layer dynamics,turbulent mixing,and pollutant dispersion,providing invaluable data for validating chemical transport models.Key findings from the tower’s research include the identification of positive feedback mechanisms between aerosols and the boundary layer,the characterization of pollutant sources and transport pathways,the determination of fluxes of gaseous and particulate species,and the assessment of the effectiveness of pollution control measures.Additionally,isotopic measurements have provided new insights into the sources and formation processes of particulate matter and reactive nitrogen species.Finally,the paper outlines future directions for tower-based research,emphasizing the need for long-term comprehensive measurements,the development of innovative tower platforms,and integration of emerging technologies.
