Let F be a number field and p be a prime. In the successive approximation theorem, we prove that, for each integer n ≥ 1, finitely many candidates for the Galois group of the nth stage of the p-class tower over F are...Let F be a number field and p be a prime. In the successive approximation theorem, we prove that, for each integer n ≥ 1, finitely many candidates for the Galois group of the nth stage of the p-class tower over F are determined by abelian type invariants of p-class groups C1pE of unramified extensions E/F with degree [E : F] = pn-1. Illustrated by the most extensive numerical results available currently, the transfer kernels (TE, F) of the p-class extensions TE, F : C1pF → C1pE from F to unramified cyclic degree-p extensions E/F are shown to be capable of narrowing down the number of contestants significantly. By determining the isomorphism type of the maximal subgroups S G of all 3-groups G with coclass cc(G) = 1, and establishing a general theorem on the connection between the p-class towers of a number field F and of an unramified abelian p-extension E/F, we are able to provide a theoretical proof of the realization of certain 3-groups S with maximal class by 3-tower groups of dihedral fields E with degree 6, which could not be realized up to now.展开更多
The International Maritime Organization(IMO)aims to reduce shipping greenhouse gas emissions by 70%by 2050,positioning onboard carbon capture(OCC)systems as essential tools,with chemical absorption being particularly ...The International Maritime Organization(IMO)aims to reduce shipping greenhouse gas emissions by 70%by 2050,positioning onboard carbon capture(OCC)systems as essential tools,with chemical absorption being particularly favorable due to its retrofit viability.This review analyzes advancements in chemical absorption technologies specific to shipborne applications,focusing on absorbent development,absorption tower optimization,and system integration.This article begins with an overview of OCC principles and advantages,followed by a discussion of technological progress,including feasibility studies and project outcomes.It explores various chemical absorbents,assessing performance,degradation,and emissions.The structural configurations of absorption towers and their modeling techniques are examined,alongside challenges such as limited vessel space,energy constraints,and gas-liquid distribution inefficiencies.Future directions emphasize the need for innovative absorbent designs,advanced simulation for tower optimization,and enhanced integration with ship energy systems,including renewable energy and waste heat recovery.The potential for intelligent technologies to enable real-time monitoring and automated management of carbon capture systems is highlighted.Finally,further investigations into fundamental interfaces and reaction kinetics are essential for advancing shipborne carbon capture technologies,providing a crucial reference for researchers and practitioners in the field.展开更多
To address the challenges of multi-scale differences,complex background interference,and unstable small target positioning in visual inspection of power towers,the existing methods still face issues such as insufficie...To address the challenges of multi-scale differences,complex background interference,and unstable small target positioning in visual inspection of power towers,the existing methods still face issues such as insufficient feature interaction and unstable confidence estimation,which lead to performance degradation in complex backgrounds and occlusion conditions.This paper proposes a precise inspection method for key power tower components using autonomous drone positioning.To this end,this paper makes three key improvements to the you only look once version 11(YOLOv11)framework.First,it constructs C3k2-adaptive multi-receptive field block(C3k2-AMRB),combining multiple dilated convolutions with a reparameterization mechanism to significantly expand the receptive field and enhance multi-scale feature extraction.Second,it designs a hierarchical wavelet interaction unit(HWIU),which leverages high-and low-frequency decomposition and reconstruction of wavelet transform(WT)to achieve cross-scale semantic alignment,enhancing feature discriminability in complex backgrounds.Third,it proposes a distribution-aware confidence refinement head(DACR-Head),which adaptively calibrates classification confidence based on the statistical characteristics of the predicted bounding-box corner distribution,improving the localization stability and accuracy of small targets.Experiments on the inspection of power line assets dataset(InsPLAD)dataset show that the integrated approach achieves a component detection accuracy at intersection over union(IoU)=0.5(CDA_(50))of 88.3%and a component detection robustness(CDR_(50:95))of 69.8%,respectively,improvements of 4.4%and 7.0%over the baseline.展开更多
"Problem of Towers of Hanoi",用递归的方法能很容易地解决问题,不用递归的方法将会是比较困难,因为随着参与盘子数的不断增多,计算时间和复杂度将会不断增多。运用仿真软件能清晰地勾勒出每个盘子的移动轨迹并给出详细的移..."Problem of Towers of Hanoi",用递归的方法能很容易地解决问题,不用递归的方法将会是比较困难,因为随着参与盘子数的不断增多,计算时间和复杂度将会不断增多。运用仿真软件能清晰地勾勒出每个盘子的移动轨迹并给出详细的移动步骤,这将会使此问题能更形象、更直观的解决。展开更多
The wind energy industry has been growing rapidly during the past decades.Along with this growth,engineering problems have gradually emerged in the wind power industry,including those related to the structural reliabi...The wind energy industry has been growing rapidly during the past decades.Along with this growth,engineering problems have gradually emerged in the wind power industry,including those related to the structural reliability of turbine towers.This study proposes a rapid seismic analysis methodology for existing wind turbine tower structures.The method is demonstrated and validated using a case study on a 1.5 MW tubular steel wind turbine tower.Three finite element(FE)models are developed first.Field tests are conducted to obtain the turbine tower’s vibrational characteristics.The tests include(1) remotely measuring the tower vibration frequencies using a long range laser Doppler Vibrometer and(2) monitoring the tower structural vibration by mounting accelerometers along the height of the tubular structure.In-situ measurements are used to validate and update the FE models of the wind turbine tower.With the updated FE model that represents the practical structural conditions,seismic analyses are performed to study the structural failure,which is defined by the steel yielding of the tubular tower.This research is anticipated to benefit the management of the increasing number of wind energy converters by providing an understanding of the seismic assessment of existing tubular steel wind turbine towers.展开更多
This article reports the findings on the adverse effect of the crosswind on the performance of natural draft cooling towers through numerical computation with the k-epsilon eddy-viscosity turbulence model. It is obser...This article reports the findings on the adverse effect of the crosswind on the performance of natural draft cooling towers through numerical computation with the k-epsilon eddy-viscosity turbulence model. It is observed here that the cause of the adverse effect of the crosswind on the cooling towers call be attributed to the around flow effect which destroys the radial inflow into the cooling towers when the wind is absent. Hence, a significant deterioration in the heat transfer from the heat exchangers at lateral sides occurs.展开更多
The structure and organization of the extreme-rain-producing deep convection towers and their roles in the formation of a southwest vortex(SWV)event are studied using the intensified surface rainfall observations,weat...The structure and organization of the extreme-rain-producing deep convection towers and their roles in the formation of a southwest vortex(SWV)event are studied using the intensified surface rainfall observations,weather radar data and numerical simulations from a high-resolution convection-allowing model.The deep convection towers occurred prior to the emergence of SWV and throughout its onset and development stages.They largely resemble the vortical hot tower(VHT)commonly seen in typhoons or hurricanes and are thus considered as a special type of VHT(sVHT).Each sVHT presented a vorticity dipole structure,with the upward motion not superpose the positive vorticity.A positive feedback process in the SWV helped the organization of sVHTs,which in turn strengthened the initial disturbance and development of SWV.The meso-γ-scale large-value areas of positive relative vorticity in the mid-toupper troposphere were largely induced by the diabatic heating and tilting.The strong mid-level convergence was attributed to the mid-level vortex enhancement.The low-level vortex intensification was mainly due to low-level convergence and the stretching of upward flow.The meso-α-scale large-value areas of positive relative vorticity in the low-level could expand up to about 400 hPa,and gradually weakened with time and height due to the decaying low-level convergence and vertical stretching in the matured SWV.As the SWV matured,two secondary circulations were formed,with a weaker mean radial inflow than the outflow and elevated to 300-400 hPa.展开更多
Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formula...Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads(ESWLSs)were derived based on structural dynamics and random vibration theory.The consistent coupled method(CCM)was presented to compensate the coupled term between background and resonant response.Taking the super-large cooling tower(H=215 m)of nuclear power plant in Jiangxi Province,China,which is the highest and largest in China,as the example,based on modified equivalent beam-net design method,the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out.Then,combining wind tunnel test and CCM,the effects of self-excited force on the surface pressures and wind-induced responses are discussed,and the wind-induced response characteristics of background component,resonant component,coupled term between background and resonant response,fluctuating responses,and wind vibration coefficients are discussed.It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.展开更多
A cloud-resolving model simulation of a mesoscale convective system （MCS） producing torrential rainfall is performed with the finest horizontal resolution of 444 m. It is shown that the model reproduces the observed...A cloud-resolving model simulation of a mesoscale convective system （MCS） producing torrential rainfall is performed with the finest horizontal resolution of 444 m. It is shown that the model reproduces the observed MCS, including its rainfall distribution and amounts, as well as the timing and location of leading rainbands and trailing stratiform clouds. Results show that discrete convective hot towers, shown in Vis5D at a scale of 2-5 kin, are triggered by evaporatively driven cold outflows converging with the high-θe air ahead. Then, they move rearward, with respect to the leading rainbands, to form stratiform clouds. These convective towers generate vortical tubes of opposite signs, with more intense cyclonic vorticity occurring in the leading convergence zone. The results appear to have important implications for the improvement of summertime quantitative precipitation forecasts and the understanding of vortical hot towers, as well midlevel mesoscale convective vortices.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;"></span>Recent trends show that in the coming decades, Kenya’s natural resources will continue to face signifi...<div style="text-align:justify;"> <span style="font-family:Verdana;"></span>Recent trends show that in the coming decades, Kenya’s natural resources will continue to face significant pressure due to both anthropogenic and natural stressors, and this will have greater negative impacts on socio-economic development including food security and livelihoods. Understanding the impacts of these stressors is an important step to developing coping and adaptation strategies at every level. The Water Towers of Kenya play a critical role in supplying ecosystems services such as water supply, timber and non-timber forest products and regulating services such as climate and water quantity and quality. To assess the vulnerability of the Water Towers to climate change, the study adopted the IPCC AR4 framework that defines vulnerability as a function of exposure, sensitivity, and adaptive capacity. The historical trends in rainfall indicate that the three Water Towers show a declining rainfall trend during the March-April-May (MAM) main rainy season, while the October-November-December (OND) short rainy season shows an increase. The temperature patterns are consistent with the domain having a common rising trend with a rate in the range of 0.3<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C to 0.5<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C per decade. Projection analysis considered three emissions scenarios: low-emission (mitigation) scenario (RCP2.6), a medium-level emission scenario (RCP4.5), and a high-emission (business as usual) scenario (RCP8.5). The results of the high-emission scenario show that the annual temperature over the Water Towers could rise by 3.0<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C to 3.5<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C by the 2050s (2036-2065) and 3.6<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C to 4.8<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C by the 2070s (2055-2085 results not presented), relative to the baseline period 1970-2000. The findings indicate that exposure, sensitivity, and adaptive capacity vary in magnitude, as well as spatially across the Water Towers. This is reflected in the spatially variable vulnerability index across the Water Towers. Overall vulnerability will increase in the water towers leading to erosion of the resilience of the exposed ecosystems and the communities that rely on ecosystem services these landscapes provide. </div>展开更多
As inferred from earthquake engineering literature,considering soil structure interaction(SSI)effects is important in evaluating the response of transmission line towers(TLT)to dynamic loads such as impulse loads.The ...As inferred from earthquake engineering literature,considering soil structure interaction(SSI)effects is important in evaluating the response of transmission line towers(TLT)to dynamic loads such as impulse loads.The proposed study investigates the dynamic effects of SSI on TLT behavior.Linear and non-linearmodels are studied.In the linearmodel,the soil is represented by complex impedances,dependent of dynamic frequency,determined from numerical simulations.The nonlinearmodel considers the soil non-linear behavior in its material constitutive law and foundation uplift in a non-linear time history analysis.The simplified structure behavior of a typical lattice transmission tower is assessed.The analysis of frequency and time domain are followed through varying soil stiffness and damping values.Three different shock durations are investigated.The soil-structure system with equivalent dynamic properties is determined.The behaviors achieved utilizing a rigid and a flexible base for the structures is compared to estimate the impact of taking SSI into account in the calculation.The current mainstream approach in structural engineering,emphasizing the importance of the SSI effect,is illustrated using an example where the SSI effect could be detrimental to the structure.Furthermore,the non-linear analysis results are analyzed to show the linear approach’s limitations in the event of grand deformations.展开更多
We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1 000 kV transmission line project in P. R. China. The height of the cup t...We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1 000 kV transmission line project in P. R. China. The height of the cup tower is 181 m with a ground elevation of 47 m, which makes it a super flexible and wind-sensitive structure. Therefore, we should analyze the wind- resistant capacity of the system. We simulated applicable transverse fluctuating wind velocity field, developed a lead-rubber damper （LRD） for controlling wind-induced vibration of long-span transmission towers, deduced LRD calculation model parameter, and researched the best layout scheme and installation method of LRD. To calculate the wind-induced response of tower-line coupling system in seven layout schemes, we used the time history analysis method, and obtained the efficiencies of wind-induced vibration control. LRD deformation research proved that the damp of all LRDs was efficient under the designed wind velocity when they were laid along the edge of tower heads. We studied the controlling efficiency resulting fTom only applying stiffness to the tower polos where the dampers used to be laid under the designed wind velocity. The results show that the controlling efficiency was not ideal when the stiffness is increased on the poles only. Therefore, LRD should conlxibute to both the stiffness and damp of a structure to effectively reduce the dynamic response of a tower-line coupling system under strong winds. We also discussed the controlling efficiency of LRD under static winds. The results show that there was little difference between displacements derived by the finite clement time history method and those obtained by static wind method conducted by a design institute. This means the simulation on space relevant wind velocity field was accurate and reasonable.展开更多
The Comoros is an archipelago in the Indian Ocean located in the Mozambique Channel between the African continent and Madagascar. Geographically Comoros is composed of four islands: Grande Comores, Anjouan, Mohél...The Comoros is an archipelago in the Indian Ocean located in the Mozambique Channel between the African continent and Madagascar. Geographically Comoros is composed of four islands: Grande Comores, Anjouan, Mohéli and Mayotte (under French administration). Apart from Mayotte, the others three independent islands commonly known as the Union of the Comoros are suffering from energy stress since their independence year 1975 until nowadays. The energy supplied and distributed by the national electricity company, SONELEC produced by diesel engines, is not stable with so much load shedding all the time. This instability energy leads to a lack of a phone network in some telecommunications towers connected to grid. The majority of telecommunications towers are located in rural areas not connected to grid and running on diesel generators, which once again leads to a problem with the telecommunications network when diesel engines fail. The two competing companies which operate in the field of telecommunications in the Comoros, namely Comores Télécom, a national public company and Telma, the private one, are still unable to ensure the provision of the telecommunications network on a regular basis. This is why we propose in the present work, a sizing of hybrid system composed essentially of a diesel generator, a wind turbine and a photovoltaic solar system with storage in batteries for supplying telecommunications towers in order to permanently ensure the provision of the telecommunications network for the well-being of the population. Our future energy must be based on non-polluting energies with significant resources. Renewable energies are the best candidates but with intermittent production especially in rural areas not connected to the national electricity grid whose energy demand is more important to meet the needs of the population. The aim of this work is the sizing of a hybrid system composed of a diesel generator, a wind turbine and a photovoltaic solar system with storage in batteries for supplying telecommunications towers located in rural areas in the Comoros. In fact, to verify the performance of the hybrid system, a numerical study has been carried out with the HOMER 2.68 Beta software using meteorological data from the Comoros. The results obtained show that this hybrid combination is more profitable in the margin of economic cost and environmental assessments with a less expensive investment. These results also show a better optimization of Wind/PV/Battery of the hybrid system used, satisfying the demand and contributing to the preservation of the environment to fight against climate change with a low cost of energy.展开更多
As one of the main load-carrying components of cable-stayed bridges,bridge towers are typically required to remain elastic even when subjected to severe ground motions with a 2%-3%probability of exceedance in 50 years...As one of the main load-carrying components of cable-stayed bridges,bridge towers are typically required to remain elastic even when subjected to severe ground motions with a 2%-3%probability of exceedance in 50 years.To fulfill this special requirement imposed by current seismic design codes,reinforcement ratios in the bridge towers have to be kept significantly higher than if limited ductility behavior of the tower is allowed.In addition,since the foundation capacity is closely related to the moment and shear capacities of the bridge tower,a large increase in bridge construction cost for elastically designed cable-stayed bridge is inevitable.To further investigate the possibility of limited ductility bridge tower design strategies,a new 1/20-scale cable-stayed bridge model with H-shaped bridge towers designed according to strong strut-weak tower column design was tested.The shake table experimental results are compared with a previous strong tower column-weak strut designed full bridge model.A comparison of the results show that ductility design with plastic hinges located on tower columns,i.e.,strong strut-weak tower column design,is another effective seismic design strategy that results in only small residual displacement at the top of the tower column,even under very severe earthquake excitations.展开更多
The typical location and number of anemometer towers in the assessed area are the key to the accuracy of wind resource assessment in complex topography.As calculation examples,this paper used two typical complex topog...The typical location and number of anemometer towers in the assessed area are the key to the accuracy of wind resource assessment in complex topography.As calculation examples,this paper used two typical complex topography wind farms in Guangxi,Yunnan province in China.Firstly,we simulated the wind resource status of the anemometer tower in the Meteodyn WT software.Secondly,we compared the simulated wind resource with the actual measured data by the anemometer tower in the same situation.Thirdly,we analyzed the influence of anemometer tower location and quantity in the accuracy of wind resource assessment through the comparison results.The results showed that the range which the anemometer tower can represent is limited(<5 kilometers),and the prediction error more than 5%.Besides,the anemometer towers in special terrain areas(such as wind acceleration areas)cannot be used as a representative choice.The relative error of the simulated average annual wind speed by choose different number of anemometer towers is about 4%,and the grid-connected power generation more than 6%.The representative effect of anemometer towers is of crucial for improving the accuracy of wind resource assessment in engineering applications.展开更多
Let p be a prime and K be a number field with non-trivial p-class group ClpK. A crucial step in identifying the Galois group G∞p of the maximal unramified pro-p extension of K is to determine its two-stage approximat...Let p be a prime and K be a number field with non-trivial p-class group ClpK. A crucial step in identifying the Galois group G∞p of the maximal unramified pro-p extension of K is to determine its two-stage approximation M=G2pk, that is the second derived quotient M≃G/Gn. The family τ1K of abelian type invariants of the p-class groups ClpL of all unramified cyclic extensions L/K of degree p is called the index- abelianization data (IPAD) of K. It is able to specify a finite batch of contestants for the second p-class group M of K. In this paper we introduce two different kinds of generalized IPADs for obtaining more sophisticated results. The multi-layered IPAD (τ1Kτ(2)K) includes data on unramified abelian extensions L/K of degree p2 and enables sharper bounds for the order of M in the case Clpk≃(p,p,p), where current im-plementations of the p-group generation algorithm fail to produce explicit contestants for M , due to memory limitations. The iterated IPAD of second order τ(2)K contains information on non-abelian unramified extensions L/K of degree p2, or even p3, and admits the identification of the p-class tower group G for various infinite series of quadratic fields K=Q(√d) with ClpK≃(p,p) possessing a p-class field tower of exact length lpK=3 as a striking novelty.展开更多
Recent examples of periodic bifurcations in descendant trees of finite p-groups with ?are used to show that the possible p-class tower groups G of certain multiquadratic fields K with p- class group of type (2,2,2) , ...Recent examples of periodic bifurcations in descendant trees of finite p-groups with ?are used to show that the possible p-class tower groups G of certain multiquadratic fields K with p- class group of type (2,2,2) , resp. (3,3), form periodic sequences in the descendant tree of the elementary Abelian root , resp. . The particular vertex of the periodic sequence which occurs as the p-class tower group G of an assigned field K is determined uniquely by the p-class number of a quadratic, resp. cubic, auxiliary field k, associated unambiguously to K. Consequently, the hard problem of identifying the p-class tower group G is reduced to an easy computation of low degree arithmetical invariants.展开更多
The well-known tower theorem of groups （resp. Lie algebras） shows that the tower of automorphism groups （resp. derivation algebras） of a finite group （resp. a finite dimensional Lie algebra） with trivial center ...The well-known tower theorem of groups （resp. Lie algebras） shows that the tower of automorphism groups （resp. derivation algebras） of a finite group （resp. a finite dimensional Lie algebra） with trivial center terminates after finitely many steps. We generalize these results for Lie rings, and present some necessary and sufficient conditions for Lie rings to be complete.展开更多
Let p be a prime. For any finite p-group G, the deep transfers T H,G ' : H / H ' → G ' / G " from the maximal subgroups H of index (G:H) = p in G to the derived subgroup G ' are introduced as an ...Let p be a prime. For any finite p-group G, the deep transfers T H,G ' : H / H ' → G ' / G " from the maximal subgroups H of index (G:H) = p in G to the derived subgroup G ' are introduced as an innovative tool for identifying G uniquely by means of the family of kernels ùd(G) =(ker(T H,G ')) (G: H) = p. For all finite 3-groups G of coclass cc(G) = 1, the family ùd(G) is determined explicitly. The results are applied to the Galois groups G =Gal(F3 (∞)/ F) of the Hilbert 3-class towers of all real quadratic fields F = Q(√d) with fundamental discriminants d > 1, 3-class group Cl3(F) □ C3 × C3, and total 3-principalization in each of their four unramified cyclic cubic extensions E/F. A systematic statistical evaluation is given for the complete range 1 d 7, and a few exceptional cases are pointed out for 1 d 8.展开更多
During ground faults on transmission lines,a number of towers near the fault are likely to acquire high potentials to ground.These tower voltages,if excessive,may present a hazard to humans and animals.This paper pres...During ground faults on transmission lines,a number of towers near the fault are likely to acquire high potentials to ground.These tower voltages,if excessive,may present a hazard to humans and animals.This paper presents analytical methods in order to determine the transmission towers potentials during ground faults,for long and short lines.The author developed a global systematic approach to calculate these voltages,which are dependent of a number of factors.Some of the most important factors are:magnitudes of fault currents,fault location with respect to the line terminals,conductor arrangement on the tower and the location of the faulted phase,the ground resistance of the faulted tower,soil resistivity,number,material and size of ground wires.The effects of these factors on the faulted tower voltages have been also examined for different types of power lines.展开更多
文摘Let F be a number field and p be a prime. In the successive approximation theorem, we prove that, for each integer n ≥ 1, finitely many candidates for the Galois group of the nth stage of the p-class tower over F are determined by abelian type invariants of p-class groups C1pE of unramified extensions E/F with degree [E : F] = pn-1. Illustrated by the most extensive numerical results available currently, the transfer kernels (TE, F) of the p-class extensions TE, F : C1pF → C1pE from F to unramified cyclic degree-p extensions E/F are shown to be capable of narrowing down the number of contestants significantly. By determining the isomorphism type of the maximal subgroups S G of all 3-groups G with coclass cc(G) = 1, and establishing a general theorem on the connection between the p-class towers of a number field F and of an unramified abelian p-extension E/F, we are able to provide a theoretical proof of the realization of certain 3-groups S with maximal class by 3-tower groups of dihedral fields E with degree 6, which could not be realized up to now.
基金supported by the National Natural Science Foundation of China(51876118)。
文摘The International Maritime Organization(IMO)aims to reduce shipping greenhouse gas emissions by 70%by 2050,positioning onboard carbon capture(OCC)systems as essential tools,with chemical absorption being particularly favorable due to its retrofit viability.This review analyzes advancements in chemical absorption technologies specific to shipborne applications,focusing on absorbent development,absorption tower optimization,and system integration.This article begins with an overview of OCC principles and advantages,followed by a discussion of technological progress,including feasibility studies and project outcomes.It explores various chemical absorbents,assessing performance,degradation,and emissions.The structural configurations of absorption towers and their modeling techniques are examined,alongside challenges such as limited vessel space,energy constraints,and gas-liquid distribution inefficiencies.Future directions emphasize the need for innovative absorbent designs,advanced simulation for tower optimization,and enhanced integration with ship energy systems,including renewable energy and waste heat recovery.The potential for intelligent technologies to enable real-time monitoring and automated management of carbon capture systems is highlighted.Finally,further investigations into fundamental interfaces and reaction kinetics are essential for advancing shipborne carbon capture technologies,providing a crucial reference for researchers and practitioners in the field.
基金supported by the National Natural Science Foundation of China(No.61702347)Hebei Academy of Sciences Basic Research Operating Fund Project(No.2025PF21)。
文摘To address the challenges of multi-scale differences,complex background interference,and unstable small target positioning in visual inspection of power towers,the existing methods still face issues such as insufficient feature interaction and unstable confidence estimation,which lead to performance degradation in complex backgrounds and occlusion conditions.This paper proposes a precise inspection method for key power tower components using autonomous drone positioning.To this end,this paper makes three key improvements to the you only look once version 11(YOLOv11)framework.First,it constructs C3k2-adaptive multi-receptive field block(C3k2-AMRB),combining multiple dilated convolutions with a reparameterization mechanism to significantly expand the receptive field and enhance multi-scale feature extraction.Second,it designs a hierarchical wavelet interaction unit(HWIU),which leverages high-and low-frequency decomposition and reconstruction of wavelet transform(WT)to achieve cross-scale semantic alignment,enhancing feature discriminability in complex backgrounds.Third,it proposes a distribution-aware confidence refinement head(DACR-Head),which adaptively calibrates classification confidence based on the statistical characteristics of the predicted bounding-box corner distribution,improving the localization stability and accuracy of small targets.Experiments on the inspection of power line assets dataset(InsPLAD)dataset show that the integrated approach achieves a component detection accuracy at intersection over union(IoU)=0.5(CDA_(50))of 88.3%and a component detection robustness(CDR_(50:95))of 69.8%,respectively,improvements of 4.4%and 7.0%over the baseline.
基金National Natural Science Foundation of China under Grant No.51208382Shanghai Science Foundation under Grant No.12ZR1433500+4 种基金Shanghai Pujiang Scholar Program under Grant No.13PJ1407900Specialized Research Fund for the Doctoral Program of Higher Education under Grant No.20120072120001State Key Laboratory of Power Transmission Equipment&System Security and New Technology under Grant No.2007DA10512711414State Key Laboratory of Disaster Reduction in Civil Engineering under Grant No.SLDRCE14-B-02Tongji University Testing Facility Funding under Grant No.2012096
文摘The wind energy industry has been growing rapidly during the past decades.Along with this growth,engineering problems have gradually emerged in the wind power industry,including those related to the structural reliability of turbine towers.This study proposes a rapid seismic analysis methodology for existing wind turbine tower structures.The method is demonstrated and validated using a case study on a 1.5 MW tubular steel wind turbine tower.Three finite element(FE)models are developed first.Field tests are conducted to obtain the turbine tower’s vibrational characteristics.The tests include(1) remotely measuring the tower vibration frequencies using a long range laser Doppler Vibrometer and(2) monitoring the tower structural vibration by mounting accelerometers along the height of the tubular structure.In-situ measurements are used to validate and update the FE models of the wind turbine tower.With the updated FE model that represents the practical structural conditions,seismic analyses are performed to study the structural failure,which is defined by the steel yielding of the tubular tower.This research is anticipated to benefit the management of the increasing number of wind energy converters by providing an understanding of the seismic assessment of existing tubular steel wind turbine towers.
基金The project supported by the National Natural Science Foundation of China (19725208) and the National Climbing project of China
文摘This article reports the findings on the adverse effect of the crosswind on the performance of natural draft cooling towers through numerical computation with the k-epsilon eddy-viscosity turbulence model. It is observed here that the cause of the adverse effect of the crosswind on the cooling towers call be attributed to the around flow effect which destroys the radial inflow into the cooling towers when the wind is absent. Hence, a significant deterioration in the heat transfer from the heat exchangers at lateral sides occurs.
基金Operational Technology Research Team Project of Chongqing Meteorological Service(YWGGTD-201702)Technology Innovation and Application Development Key Project of Chongqing(cstc2019jscx-tjsb X0007)Natural Science Foundation of Chongqing(cstc2018jcyj AX0434)。
文摘The structure and organization of the extreme-rain-producing deep convection towers and their roles in the formation of a southwest vortex(SWV)event are studied using the intensified surface rainfall observations,weather radar data and numerical simulations from a high-resolution convection-allowing model.The deep convection towers occurred prior to the emergence of SWV and throughout its onset and development stages.They largely resemble the vortical hot tower(VHT)commonly seen in typhoons or hurricanes and are thus considered as a special type of VHT(sVHT).Each sVHT presented a vorticity dipole structure,with the upward motion not superpose the positive vorticity.A positive feedback process in the SWV helped the organization of sVHTs,which in turn strengthened the initial disturbance and development of SWV.The meso-γ-scale large-value areas of positive relative vorticity in the mid-toupper troposphere were largely induced by the diabatic heating and tilting.The strong mid-level convergence was attributed to the mid-level vortex enhancement.The low-level vortex intensification was mainly due to low-level convergence and the stretching of upward flow.The meso-α-scale large-value areas of positive relative vorticity in the low-level could expand up to about 400 hPa,and gradually weakened with time and height due to the decaying low-level convergence and vertical stretching in the matured SWV.As the SWV matured,two secondary circulations were formed,with a weaker mean radial inflow than the outflow and elevated to 300-400 hPa.
基金Projects(50978203,51208254)supported by the National Natural Science Foundation of ChinaProject(BK2012390)supported by Natural Science Foundation of Jiangsu Province,ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Traditional gust load factor(GLF)method,inertial wind load(IWL)method and tri-component method(LRC+IWL)cannot accurately analyze the wind-induced responses of super-large cooling towers,so the real combination formulas of fluctuating wind-induced responses and equivalent static wind loads(ESWLSs)were derived based on structural dynamics and random vibration theory.The consistent coupled method(CCM)was presented to compensate the coupled term between background and resonant response.Taking the super-large cooling tower(H=215 m)of nuclear power plant in Jiangxi Province,China,which is the highest and largest in China,as the example,based on modified equivalent beam-net design method,the aero-elastic model for simultaneous pressure and vibration measurement of super-large cooling tower is firstly carried out.Then,combining wind tunnel test and CCM,the effects of self-excited force on the surface pressures and wind-induced responses are discussed,and the wind-induced response characteristics of background component,resonant component,coupled term between background and resonant response,fluctuating responses,and wind vibration coefficients are discussed.It can be concluded that wind-induced response mechanism must be understood to direct the wind resistant design for super-large cooling towers.
基金supported by Jiangsu Education Science Foundation (Grant No.07KJB170065)Chinese National Science Foundation (Grant No.40775060)U.S.National Science Foundation (Grant No.ATM0758609)
文摘A cloud-resolving model simulation of a mesoscale convective system （MCS） producing torrential rainfall is performed with the finest horizontal resolution of 444 m. It is shown that the model reproduces the observed MCS, including its rainfall distribution and amounts, as well as the timing and location of leading rainbands and trailing stratiform clouds. Results show that discrete convective hot towers, shown in Vis5D at a scale of 2-5 kin, are triggered by evaporatively driven cold outflows converging with the high-θe air ahead. Then, they move rearward, with respect to the leading rainbands, to form stratiform clouds. These convective towers generate vortical tubes of opposite signs, with more intense cyclonic vorticity occurring in the leading convergence zone. The results appear to have important implications for the improvement of summertime quantitative precipitation forecasts and the understanding of vortical hot towers, as well midlevel mesoscale convective vortices.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;"></span>Recent trends show that in the coming decades, Kenya’s natural resources will continue to face significant pressure due to both anthropogenic and natural stressors, and this will have greater negative impacts on socio-economic development including food security and livelihoods. Understanding the impacts of these stressors is an important step to developing coping and adaptation strategies at every level. The Water Towers of Kenya play a critical role in supplying ecosystems services such as water supply, timber and non-timber forest products and regulating services such as climate and water quantity and quality. To assess the vulnerability of the Water Towers to climate change, the study adopted the IPCC AR4 framework that defines vulnerability as a function of exposure, sensitivity, and adaptive capacity. The historical trends in rainfall indicate that the three Water Towers show a declining rainfall trend during the March-April-May (MAM) main rainy season, while the October-November-December (OND) short rainy season shows an increase. The temperature patterns are consistent with the domain having a common rising trend with a rate in the range of 0.3<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C to 0.5<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C per decade. Projection analysis considered three emissions scenarios: low-emission (mitigation) scenario (RCP2.6), a medium-level emission scenario (RCP4.5), and a high-emission (business as usual) scenario (RCP8.5). The results of the high-emission scenario show that the annual temperature over the Water Towers could rise by 3.0<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C to 3.5<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C by the 2050s (2036-2065) and 3.6<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C to 4.8<span style="color:#4F4F4F;font-family:-apple-system, "font-size:14px;white-space:normal;background-color:#FFFFFF;">°</span>C by the 2070s (2055-2085 results not presented), relative to the baseline period 1970-2000. The findings indicate that exposure, sensitivity, and adaptive capacity vary in magnitude, as well as spatially across the Water Towers. This is reflected in the spatially variable vulnerability index across the Water Towers. Overall vulnerability will increase in the water towers leading to erosion of the resilience of the exposed ecosystems and the communities that rely on ecosystem services these landscapes provide. </div>
基金This work was financed by The Natural Sciences and Engineering Research Council of Canada(NSERC)and Hydro-Québec Transénergy(HQTE).
文摘As inferred from earthquake engineering literature,considering soil structure interaction(SSI)effects is important in evaluating the response of transmission line towers(TLT)to dynamic loads such as impulse loads.The proposed study investigates the dynamic effects of SSI on TLT behavior.Linear and non-linearmodels are studied.In the linearmodel,the soil is represented by complex impedances,dependent of dynamic frequency,determined from numerical simulations.The nonlinearmodel considers the soil non-linear behavior in its material constitutive law and foundation uplift in a non-linear time history analysis.The simplified structure behavior of a typical lattice transmission tower is assessed.The analysis of frequency and time domain are followed through varying soil stiffness and damping values.Three different shock durations are investigated.The soil-structure system with equivalent dynamic properties is determined.The behaviors achieved utilizing a rigid and a flexible base for the structures is compared to estimate the impact of taking SSI into account in the calculation.The current mainstream approach in structural engineering,emphasizing the importance of the SSI effect,is illustrated using an example where the SSI effect could be detrimental to the structure.Furthermore,the non-linear analysis results are analyzed to show the linear approach’s limitations in the event of grand deformations.
基金Funded by the Science and Technology Research Project of the State Grid Corporation (No. [2007]413)
文摘We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1 000 kV transmission line project in P. R. China. The height of the cup tower is 181 m with a ground elevation of 47 m, which makes it a super flexible and wind-sensitive structure. Therefore, we should analyze the wind- resistant capacity of the system. We simulated applicable transverse fluctuating wind velocity field, developed a lead-rubber damper （LRD） for controlling wind-induced vibration of long-span transmission towers, deduced LRD calculation model parameter, and researched the best layout scheme and installation method of LRD. To calculate the wind-induced response of tower-line coupling system in seven layout schemes, we used the time history analysis method, and obtained the efficiencies of wind-induced vibration control. LRD deformation research proved that the damp of all LRDs was efficient under the designed wind velocity when they were laid along the edge of tower heads. We studied the controlling efficiency resulting fTom only applying stiffness to the tower polos where the dampers used to be laid under the designed wind velocity. The results show that the controlling efficiency was not ideal when the stiffness is increased on the poles only. Therefore, LRD should conlxibute to both the stiffness and damp of a structure to effectively reduce the dynamic response of a tower-line coupling system under strong winds. We also discussed the controlling efficiency of LRD under static winds. The results show that there was little difference between displacements derived by the finite clement time history method and those obtained by static wind method conducted by a design institute. This means the simulation on space relevant wind velocity field was accurate and reasonable.
文摘The Comoros is an archipelago in the Indian Ocean located in the Mozambique Channel between the African continent and Madagascar. Geographically Comoros is composed of four islands: Grande Comores, Anjouan, Mohéli and Mayotte (under French administration). Apart from Mayotte, the others three independent islands commonly known as the Union of the Comoros are suffering from energy stress since their independence year 1975 until nowadays. The energy supplied and distributed by the national electricity company, SONELEC produced by diesel engines, is not stable with so much load shedding all the time. This instability energy leads to a lack of a phone network in some telecommunications towers connected to grid. The majority of telecommunications towers are located in rural areas not connected to grid and running on diesel generators, which once again leads to a problem with the telecommunications network when diesel engines fail. The two competing companies which operate in the field of telecommunications in the Comoros, namely Comores Télécom, a national public company and Telma, the private one, are still unable to ensure the provision of the telecommunications network on a regular basis. This is why we propose in the present work, a sizing of hybrid system composed essentially of a diesel generator, a wind turbine and a photovoltaic solar system with storage in batteries for supplying telecommunications towers in order to permanently ensure the provision of the telecommunications network for the well-being of the population. Our future energy must be based on non-polluting energies with significant resources. Renewable energies are the best candidates but with intermittent production especially in rural areas not connected to the national electricity grid whose energy demand is more important to meet the needs of the population. The aim of this work is the sizing of a hybrid system composed of a diesel generator, a wind turbine and a photovoltaic solar system with storage in batteries for supplying telecommunications towers located in rural areas in the Comoros. In fact, to verify the performance of the hybrid system, a numerical study has been carried out with the HOMER 2.68 Beta software using meteorological data from the Comoros. The results obtained show that this hybrid combination is more profitable in the margin of economic cost and environmental assessments with a less expensive investment. These results also show a better optimization of Wind/PV/Battery of the hybrid system used, satisfying the demand and contributing to the preservation of the environment to fight against climate change with a low cost of energy.
基金National Key Research and Development Plan,China under Grant No.2017YFC1500702the National Natural Science Foundation of China under Grant No.51478338。
文摘As one of the main load-carrying components of cable-stayed bridges,bridge towers are typically required to remain elastic even when subjected to severe ground motions with a 2%-3%probability of exceedance in 50 years.To fulfill this special requirement imposed by current seismic design codes,reinforcement ratios in the bridge towers have to be kept significantly higher than if limited ductility behavior of the tower is allowed.In addition,since the foundation capacity is closely related to the moment and shear capacities of the bridge tower,a large increase in bridge construction cost for elastically designed cable-stayed bridge is inevitable.To further investigate the possibility of limited ductility bridge tower design strategies,a new 1/20-scale cable-stayed bridge model with H-shaped bridge towers designed according to strong strut-weak tower column design was tested.The shake table experimental results are compared with a previous strong tower column-weak strut designed full bridge model.A comparison of the results show that ductility design with plastic hinges located on tower columns,i.e.,strong strut-weak tower column design,is another effective seismic design strategy that results in only small residual displacement at the top of the tower column,even under very severe earthquake excitations.
基金the financial support by the National Natural Science Foundation of China(No.52176212).
文摘The typical location and number of anemometer towers in the assessed area are the key to the accuracy of wind resource assessment in complex topography.As calculation examples,this paper used two typical complex topography wind farms in Guangxi,Yunnan province in China.Firstly,we simulated the wind resource status of the anemometer tower in the Meteodyn WT software.Secondly,we compared the simulated wind resource with the actual measured data by the anemometer tower in the same situation.Thirdly,we analyzed the influence of anemometer tower location and quantity in the accuracy of wind resource assessment through the comparison results.The results showed that the range which the anemometer tower can represent is limited(<5 kilometers),and the prediction error more than 5%.Besides,the anemometer towers in special terrain areas(such as wind acceleration areas)cannot be used as a representative choice.The relative error of the simulated average annual wind speed by choose different number of anemometer towers is about 4%,and the grid-connected power generation more than 6%.The representative effect of anemometer towers is of crucial for improving the accuracy of wind resource assessment in engineering applications.
文摘Let p be a prime and K be a number field with non-trivial p-class group ClpK. A crucial step in identifying the Galois group G∞p of the maximal unramified pro-p extension of K is to determine its two-stage approximation M=G2pk, that is the second derived quotient M≃G/Gn. The family τ1K of abelian type invariants of the p-class groups ClpL of all unramified cyclic extensions L/K of degree p is called the index- abelianization data (IPAD) of K. It is able to specify a finite batch of contestants for the second p-class group M of K. In this paper we introduce two different kinds of generalized IPADs for obtaining more sophisticated results. The multi-layered IPAD (τ1Kτ(2)K) includes data on unramified abelian extensions L/K of degree p2 and enables sharper bounds for the order of M in the case Clpk≃(p,p,p), where current im-plementations of the p-group generation algorithm fail to produce explicit contestants for M , due to memory limitations. The iterated IPAD of second order τ(2)K contains information on non-abelian unramified extensions L/K of degree p2, or even p3, and admits the identification of the p-class tower group G for various infinite series of quadratic fields K=Q(√d) with ClpK≃(p,p) possessing a p-class field tower of exact length lpK=3 as a striking novelty.
文摘Recent examples of periodic bifurcations in descendant trees of finite p-groups with ?are used to show that the possible p-class tower groups G of certain multiquadratic fields K with p- class group of type (2,2,2) , resp. (3,3), form periodic sequences in the descendant tree of the elementary Abelian root , resp. . The particular vertex of the periodic sequence which occurs as the p-class tower group G of an assigned field K is determined uniquely by the p-class number of a quadratic, resp. cubic, auxiliary field k, associated unambiguously to K. Consequently, the hard problem of identifying the p-class tower group G is reduced to an easy computation of low degree arithmetical invariants.
基金supported in part by NSFC (10371032)Doctoral Foundation of Ministry of Education(20050512002)+1 种基金Youth Foundation of Tianyuan(10726020)Youth Foundation of Hubei Provincial Department of Education(Q20081008)
文摘The well-known tower theorem of groups （resp. Lie algebras） shows that the tower of automorphism groups （resp. derivation algebras） of a finite group （resp. a finite dimensional Lie algebra） with trivial center terminates after finitely many steps. We generalize these results for Lie rings, and present some necessary and sufficient conditions for Lie rings to be complete.
文摘Let p be a prime. For any finite p-group G, the deep transfers T H,G ' : H / H ' → G ' / G " from the maximal subgroups H of index (G:H) = p in G to the derived subgroup G ' are introduced as an innovative tool for identifying G uniquely by means of the family of kernels ùd(G) =(ker(T H,G ')) (G: H) = p. For all finite 3-groups G of coclass cc(G) = 1, the family ùd(G) is determined explicitly. The results are applied to the Galois groups G =Gal(F3 (∞)/ F) of the Hilbert 3-class towers of all real quadratic fields F = Q(√d) with fundamental discriminants d > 1, 3-class group Cl3(F) □ C3 × C3, and total 3-principalization in each of their four unramified cyclic cubic extensions E/F. A systematic statistical evaluation is given for the complete range 1 d 7, and a few exceptional cases are pointed out for 1 d 8.
文摘During ground faults on transmission lines,a number of towers near the fault are likely to acquire high potentials to ground.These tower voltages,if excessive,may present a hazard to humans and animals.This paper presents analytical methods in order to determine the transmission towers potentials during ground faults,for long and short lines.The author developed a global systematic approach to calculate these voltages,which are dependent of a number of factors.Some of the most important factors are:magnitudes of fault currents,fault location with respect to the line terminals,conductor arrangement on the tower and the location of the faulted phase,the ground resistance of the faulted tower,soil resistivity,number,material and size of ground wires.The effects of these factors on the faulted tower voltages have been also examined for different types of power lines.
