With the appearance of novel radar signal with low intercept probability, the bandwidth of radar receiver is wider and wider. Wideband digital receiver becomes a research hotspot in the field of communication...With the appearance of novel radar signal with low intercept probability, the bandwidth of radar receiver is wider and wider. Wideband digital receiver becomes a research hotspot in the field of communication, radar and electronic reconnaissance, etc. As one of wideband digital receiver systems, digital channelized receiver has become a research emphasis due to the characteristics of full probability receiving and processing multiple signals. Digital channelized technology and signal sampling theory are deeply studied and an efficient channelized model is derived based on filter banks. The correctness of the model is verified by computer simulation The model has less computation compared with the traditional model, which is suitable for engineering application展开更多
The data on the hillslope and channelized debris flows in the Shitou area of central Taiwan occurred during Typhoons Toraji and Nali in 2001 were applied in this paper. The geomorphic parameters, including the flow le...The data on the hillslope and channelized debris flows in the Shitou area of central Taiwan occurred during Typhoons Toraji and Nali in 2001 were applied in this paper. The geomorphic parameters, including the flow length, gully gradient, drainage area and form factor of the debris flows were determined by spatial analysis using a Geographic Information System (GIS) based on the data derived from field investigation, aerial photographs, and topographical maps. According to such determined geomorphic parameters, the threshold conditions and empirical equations, such as the relationship between the gully gradient and drainage area and that between gully length and drainage area and topographic parameter, are presented and used to distinguish the geomorphic characteristics between the channelized and hillslope debris flows.展开更多
A novel efficient partial sharing channelization structure with odd and even stacking is designed and implemented. There are two special designs in the proposed structure. Firstly, by the intensive channel overlap des...A novel efficient partial sharing channelization structure with odd and even stacking is designed and implemented. There are two special designs in the proposed structure. Firstly, by the intensive channel overlap design, for non-cooperative wideband signals, the proposed structure can achieve good parameter estimation accuracy and high probability of complete interception.Secondly, based on the partial sharing design developed in this paper, the computation burden of the proposed structure can be greatly reduced compared with the traditional directly implemented structures. Experiments and numerical simulations are conducted to evaluate the proposed structure, which shows its improvements over traditional methods in terms of field programmable gate arrays(FPGA) resource consumption and parameter estimation accuracy.展开更多
An approach is proposed to realize a digital channelized receiver in the fractional Fourier domain （FRFD） for signal intercept applications. The presented architecture can be considered as a generalization of that i...An approach is proposed to realize a digital channelized receiver in the fractional Fourier domain （FRFD） for signal intercept applications. The presented architecture can be considered as a generalization of that in the traditional Fourier domain. Since the linear frequency modulation （LFM） signal has a good energy concentration in the FRFD, by choosing an appropriate fractional Fourier transform （FRFT） order, the presented architecture can concentrate the broadband LFM signal into only one sub-channel and that will prevent it from crossing several sub-channels. Thus the performance of the signal detection and parameter estimation after the sub-channel output will be improved significantly. The computational complexity is reduced enormously due to the implementation of the polyphase filter bank decomposition, thus the proposed architecture can be realized as efficiently as in the Fourier domain. The related simulation results are presented to verify the validity of the theories and methods involved in this paper.展开更多
For digital channelized frequency division multiple access based satellite communication(SATCOM) systems,it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously u...For digital channelized frequency division multiple access based satellite communication(SATCOM) systems,it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously under limited and non-linear high-power amplifier conditions.In this paper,different from the traditional link supportability designs aiming at minimizing the total transponder output power,a maximal sum Shannon capacity optimization objective is firstly raised subject to link supportability constraints.Furthermore,an efficient multilevel optimization(MO) algorithm is proposed to solve the considered optimization problem in the case of single link for each terminal.Moreover,in the case of multiple links for one terminal,an improved MO algorithm involving Golden section and discrete gradient searching procedures is proposed to optimize power allocation over all links.Finally,several numerical results are provided to demonstrate the effectiveness of our proposals.Comparison results show that,by the MO algorithm,not only all links' supportability can be guaranteed but also a larger sum capacity can be achieved with lower complexity.展开更多
Assessing environmental flows （e-flows） for urban rivers is important for water resources planning and river protection, Many e-flow assessment methods have been established based on species＇ habitat pro- vision re...Assessing environmental flows （e-flows） for urban rivers is important for water resources planning and river protection, Many e-flow assessment methods have been established based on species＇ habitat pro- vision requirements and pollutant dilution requirements, To avoid flood risk, however, many urban rivers have been transformed into straight, trapezoidal-profiled concrete channels, leading to the disappearance of valuable species, With the construction of water pollution-control projects, pollutant inputs into rivers have been effectively controlled in some urban rivers, For these rivers, the e-flows determined by tradi- tional methods will be very small, and will consequently lead to a low priority being given to river pro- tection in future water resources allocation and management, To more effectively assess the e-flows of channelized urban rivers, we propose three e-flow degrees, according to longitudinal hydrological con- nectivity （high, medium, and low）, in addition to the pollutant dilution water requirement determined by the mass-balance equation, In the high connectivity scenario, the intent is for the e-flows to maintain flow velocity, which can ensure the self-purification of rivers and reduce algal blooms; in the medium connectivity scenario, the intent is for the e-flows to permanently maintain the longitudinal hydrological connectivity of rivers that are isolated into several ponds by means of weirs, in order to ensure the exchange of material, energy, and information in rivers; and in the low connectivity scenario, the intent is for the e-flows to intermittently connect isolated ponds every few days （which is designed to further reduce e-flows）, The proposed methods have been used in Shiwuli River, China, to demonstrate their effectiveness, The new methods can offer more precise and realistic e-flow results and can effectively direct the construction and management of e-flow supply projects,展开更多
Most inverse reservoir modeling techniques require many forward simulations, and the posterior models cannot preserve geological features of prior models. This study proposes an iterative static modeling approach that...Most inverse reservoir modeling techniques require many forward simulations, and the posterior models cannot preserve geological features of prior models. This study proposes an iterative static modeling approach that utilizes dynamic data for rejecting an unsuitable training image(TI) among a set of TI candidates and for synthesizing history-matched pseudo-soft data. The proposed method is applied to two cases of channelized reservoirs, which have uncertainty in channel geometry such as direction, amplitude, and width. Distance-based clustering is applied to the initial models in total to select the qualified models efficiently. The mean of the qualified models is employed as a history-matched facies probability map in the next iteration of static models. Also, the most plausible TI is determined among TI candidates by rejecting other TIs during the iteration. The posterior models of the proposed method outperform updated models of ensemble Kalman filter(EnKF) and ensemble smoother(ES) because they describe the true facies connectivity with bimodal distribution and predict oil and water production with a reasonable range of uncertainty. In terms of simulation time, it requires 30 times of forward simulation in history matching, while the EnKF and ES need 9000 times and 200 times, respectively.展开更多
Granular mass flows （e.g., debris flows/avalanches） in landslide-prone areas are of great concern because they often cause catastrophic disasters as a result of their long run-out distances and large impact forces. ...Granular mass flows （e.g., debris flows/avalanches） in landslide-prone areas are of great concern because they often cause catastrophic disasters as a result of their long run-out distances and large impact forces. To investigate the factors influencing granular mass flow mobility, experimental tests were conducted in a flume model. Granular materials consisting of homogeneous sand and non- homogeneous sandy soil were used for studying particle size effects. Run-out tests with variable flow masses, water contents, and sloping channel confinement parameters were conducted as well. The results indicated that granular mass flow mobility was significantly influenced by the initial water content; a critical water content corresponding to the smallest flow mobility exists for different granular materials. An increase in the total flow mass generally induced a reduction in the travel angle （an increase in flow mobility）. Consistent with field observations, the travel angles for different granular materials decreased roughly in proportion to the logarithm of mass. The flume model tests illustrate that the measured travel angles increase as the proportion of fine particles increases. Interestingly, natural terrain possesses critical confinement characteristics for different granular mass flows.展开更多
Riparian zones of channelized agricultural streams in northwestern Mississippi typically consist of narrow vegetative corridors low in habitat diversity and lacking riparian wetlands. Land clearing practices and strea...Riparian zones of channelized agricultural streams in northwestern Mississippi typically consist of narrow vegetative corridors low in habitat diversity and lacking riparian wetlands. Land clearing practices and stream channelization have led to the development of gully erosion and further fragmentation of these degraded riparian zones. Currently, installation of a gully erosion control structure (drop pipe) at the riparian zone-agricultural field interface leads to the incidental establishment of four riparian habitat types that differ in habitat area, vegetative structure, and pool size. Small mammals were sampled within four sites of each habitat type from June 1994 to July 1995. Small mammal diversity, abundance, and hispid cotton rat (Sigmodon hispidus) weight were the least within smallest Type I habitats with the least vegetative structural diversity and were the greatest within the larger Type II, III, or IV habitats having greater vegetative structural diversity and pool size. Small mammal diversity and abundance were the least in the summer 1994, increased in the fall 1994, and then declined later in our study. Hispid cotton rat abundance was the least in summer 1994, winter 1994, and spring 1995 and was the greatest in fall 1994 and summer 1995. Our results suggest that modifying the drop pipe installation design to facilitate the development of larger riparian habitats with greater vegetative structural diversity will provide the greatest benefits for small mammals.展开更多
A structure of dynamic reconfigurable channelized filter bank is proposed in order to solve the problem that the uniform channelized receiver cannot receive the cross-channel and wideband signal. The dynamic reconfigu...A structure of dynamic reconfigurable channelized filter bank is proposed in order to solve the problem that the uniform channelized receiver cannot receive the cross-channel and wideband signal. The dynamic reconfigurable channelized filter bank is divided into two parts-the analysis filter bank and the synthesis filter bank. The function of the analysis filter bank is to divide the received signal into several sub-signals according to the channel division. Then the sub-signals of each channel need to be detected and discriminated. At last, we use the sub-signals to reconstruct the original received signal by the synthesis filter bank. The analysis filter and the synthesis filter bank of the dynamic reconfigurable channelized filter bank are all efficient polyphase structures, so it can save more hardware resources and has extensive applicability. The structure is simulated by MATLAB and the simulation results verify the correctness of this structure.展开更多
针对UAV在仿真实验中自动跟踪移动目标的需求,提出基于改进CSRT(channel and spatial reliability-aware tracker)算法的无人机长时自动跟踪方法。通过导向滤波加拉普拉斯算子LOGF(laplacian of guided filter)检测获取目标边缘特征,再...针对UAV在仿真实验中自动跟踪移动目标的需求,提出基于改进CSRT(channel and spatial reliability-aware tracker)算法的无人机长时自动跟踪方法。通过导向滤波加拉普拉斯算子LOGF(laplacian of guided filter)检测获取目标边缘特征,再与HOG(histogram of oriented gradient)和CN(color names)特征融合,增强算法对目标的判别能力;使用平均峰值相关能量和感知哈希汉明距离来综合判定目标状态,当判定目标被遮挡时,采用YOLOv8定位目标,再将定位结果传输至跟踪算法继续跟踪目标。仿真结果表明:在搭建的仿真环境中算法能够在目标被遮挡时仍能长时稳定的跟踪目标,为无人机目标跟踪算法研究提供了良好的仿真实验环境。展开更多
To enhance the efficiency of a pathogen forecasting model in the beach areas of southern Lake Michigan and to reduce the computation time, the near-shore current is approximated as a channelized flow parallel to the s...To enhance the efficiency of a pathogen forecasting model in the beach areas of southern Lake Michigan and to reduce the computation time, the near-shore current is approximated as a channelized flow parallel to the shorelines in clockwise or anti-clock- wise direction within the accuracy tolerance range. A channelized model with a curvilinear boundary can significantly reduce the computation effort, and at the same time achieve a good agreement between the predicted and measured water surface elevations, currents, and water temperatures. The sensitivity analysis results show that the suitable channel width for the near-shore region of southern Lake Michigan should be no less than 10 kin. The modeling results of the water temperature are much less sensitive to the channel width than those of the current velocity and the water surface elevation. The modeling results also show a close correlation between the speeds of the wind and the near-shore current. The current may fully respond the wind stress with a time lag of several hours. The correlation may provide an approximate estimation of the lake circulation under some wind conditions for a practical fore- casting purpose. More complex wind-current relationships need to be described with a more sophisticated hydrodynamic model. This verified model can be used for the pathogen forecasting in the near-shore regions of southern Lake Michigan in the future.展开更多
Ischemia–reperfusion injury is a common pathophysiological mechanism in retinal degeneration.PANoptosis is a newly defined integral form of regulated cell death that combines the key features of pyroptosis,apoptosis,...Ischemia–reperfusion injury is a common pathophysiological mechanism in retinal degeneration.PANoptosis is a newly defined integral form of regulated cell death that combines the key features of pyroptosis,apoptosis,and necroptosis.Oligomerization of mitochondrial voltage-dependent anion channel 1 is an important pathological event in regulating cell death in retinal ischemia–reperfusion injury.However,its role in PANoptosis remains largely unknown.In this study,we demonstrated that voltage-dependent anion channel 1 oligomerization-mediated mitochondrial dysfunction was associated with PANoptosis in retinal ischemia–reperfusion injury.Inhibition of voltage-dependent anion channel 1 oligomerization suppressed mitochondrial dysfunction and PANoptosis in retinal cells subjected to ischemia–reperfusion injury.Mechanistically,mitochondria-derived reactive oxygen species played a central role in the voltagedependent anion channel 1-mediated regulation of PANoptosis by promoting PANoptosome assembly.Moreover,inhibiting voltage-dependent anion channel 1 oligomerization protected against PANoptosis in the retinas of rats subjected to ischemia–reperfusion injury.Overall,our findings reveal the critical role of voltage-dependent anion channel 1 oligomerization in regulating PANoptosis in retinal ischemia–reperfusion injury,highlighting voltage-dependent anion channel 1 as a promising therapeutic target.展开更多
Lithium–sulfur(Li–S)batteries are promisingcandidates for next-generation energy storagegiven their high energy density and potential low cost.Chemically activated carbon(CAC)is often used fortheir cathodes,because ...Lithium–sulfur(Li–S)batteries are promisingcandidates for next-generation energy storagegiven their high energy density and potential low cost.Chemically activated carbon(CAC)is often used fortheir cathodes,because it has a high specific surfacearea for sulfur loading.We have developed a pressurizedphysical activation(PPA)method that producedan activated carbon(PPAC)with a high specific surfacearea comparable to that of CAC.The pore structure of PPAC could be changed and its use as a cathode material for Li–Sbatteries was investigated.Battery tests at different capacity rates(C-rates)showed that it had a much improved high-rate performancewith a discharge capacity of 900 mAh/(g of sulfur)at 1 C,in contrast to only 600 mAh/(g of sulfur)for CAC.Porestructure analyses showed that PPAC prepared at a high activation temperature(1000℃)had unusual channel-like mesoporesbetween the microdomains that are the basic structural units of artificial carbon materials.These are connected to microporesdeveloped in each microdomain,and deliver ions from the surroundings to the internal pores and vice versa.The well-developedmicropores and mesopores of PPAC respectively ensured the high adsorption of lithium polysulfides and a high rate ofion diffusion.Compared to CAC,PPAC is a high-performance,low-cost cathode material that is promising for use in futureLi–S batteries.展开更多
The effects of channel segregation on the macro-and micro-scale chemical composition,microstructure,hardness,and tensile deformation behavior of Ti45Nb wires were investigated.The results show that wires with severe c...The effects of channel segregation on the macro-and micro-scale chemical composition,microstructure,hardness,and tensile deformation behavior of Ti45Nb wires were investigated.The results show that wires with severe channel segregation exhibit a macroscopic chemical composition identical to those without segregation,and 3D X-ray imaging result also reveals no abnormalities.After annealing,both types of wires exhibit an equiaxed single-phase microstructure with comparable grain sizes,suggesting that channel segregation has negligible influence on the macroscopic composition and grain size.Metallographic examination reveals that channel segregation manifests as spot-like features in the transverse section and band-like structures in the longitudinal section.EDS analysis identifies these regions as Ti-enriched segregations,with a Ti content higher than that of the surrounding matrix by approximately 4.42wt%.Compared to segregation-free wires,those containing extensive channel segregation demonstrate a 15.5%increase in ultimate tensile strength and a 12.3%increase in yield strength,but suffer a reduction in elongation and reduction of area by 19.8%and 18.9%,respectively.Furthermore,the mechanical properties of wires with segregation show significant fluctuations.Fractographic analysis reveals a larger fracture surface area in segregated wires.Severe dislocation pile-ups occur at the interfaces of these segregated regions,initiating microcrack nucleation.This promotes rapid crack propagation of the Ti45Nb wire,leading to a significant decrease in plasticity and reduction of area.展开更多
Ultrafine-grained(UFG)pure titanium was produced by equal channel angular pressing for 4 passes,followed by rotatory swaging at room temperature.The strain-controlled low-cycle fatigue tests of UFG and coarse-grained(...Ultrafine-grained(UFG)pure titanium was produced by equal channel angular pressing for 4 passes,followed by rotatory swaging at room temperature.The strain-controlled low-cycle fatigue tests of UFG and coarse-grained(CG)pure titanium were conducted by Instron electro-hydraulic servo fatigue testing machine in the strain amplitude range of 0.5%—1.1%at room temperature.Transmission electron microscope(TEM)and scanning electron microscope were used to investigate the microstructure and fracture surface of UFG pure titanium after fatigue tests.Results show that UFG pure titanium exhibits a longer low-cycle fatigue life,compared with the CG pure titanium.For example,at a total strain amplitude of 0.5%,UFG and CG pure titanium has fatigue life of 10850 and 4820 cycles,respectively.Significant cyclic softening occurs in UFG pure titanium,except in the case of a total strain amplitude of 0.5%.Hysteresis loop area is increased rapidly with the increase in strain amplitude.The fracture surface shows that the fatigue crack is initiated from the specimen surface.A series of fatigue striations and many microcracks exist in the propagation region.With the increase in strain amplitude,the predominant failure mode is transformed from ductile failure into quasi-cleavage failure.Dislocation slip is the main plastic deformation mechanism of UFG pure titanium during low-cycle fatigue deformation.展开更多
Numerous pathological states of the nervous system involve alterations in neuronal excitability and synaptic dysfunction,which depend on the function of ion channels.Due to their critical involvement in health and dis...Numerous pathological states of the nervous system involve alterations in neuronal excitability and synaptic dysfunction,which depend on the function of ion channels.Due to their critical involvement in health and disease,the search for new compounds that modulate these proteins is still relevant.Traditional medicine has long been a rich source of neuroactive compounds.For example,the indigenous Mapuche people have used the leaves and bark of the Drimys winteri tree for centuries to treat various diseases.Consequently,several studies have investigated the biological effects of compounds in Drimys winteri,highlighting sesquiterpenes such asα-humulene,drimenin,polygodial,andα-,β-,γ-eudesmol.However,there is currently no literature review focusing on the ability of these sesquiterpenes to modulate ion channels.This review summarizes the current knowledge about neuroactive compounds found in Drimys winteri,with special emphasis on their direct actions on neuronal ion channels.Several Drimys winteri sesquiterpenes modulate a diverse array of neuronal ion channels,including transient receptor potential channels,gamma-aminobutyric acid A receptors,nicotinic acetylcholine receptors,and voltage-dependent Ca^(2+)and Na^(+)channels.Interestingly,the modulation of these molecular targets by Drimys winteri sesquiterpenes correlates with their therapeutic actions.The promiscuous pharmacological profile of Drimys winteri sesquiterpenes suggests they modulate multiple protein targets in vivo,making them potentially useful for treating complex,multifactorial diseases.Further studies at the molecular level may aid in developing multitargeted drugs with enhanced therapeutic effects.展开更多
The smart meter communication system has substantial application value for the construction and upgrading of the entire power system.The deployment of the transmitter(Tx)of the smart meter system in the residential sc...The smart meter communication system has substantial application value for the construction and upgrading of the entire power system.The deployment of the transmitter(Tx)of the smart meter system in the residential scenarios is vexed by the need for more theoretical support.This paper mainly studies the communication channel between the Tx at semibasement and receiver(Rx)at outdoor.The design of an effective communication system relies on an accurate understanding of channel characteristics.Channel measurements and ray-tracing channel modeling are conducted to obtain channel data.The influence of different positions at same semi-basement is studied.Typical channel characteristics are analyzed,such as power delay profile(PDP),power angular profile(PAP),root-mean-square(RMS)delay spread(DS),channel capacity,received power,and path loss.The influence of different semi-basement placements and different floor heights is also compared.Besides,the channel measurements and simulation data fit well,which can illustrate the validity and reliability of the acquired channel data.This paper can provide theoretical support for the design and optimization of smart meter communication systems in semi-basement scenarios.展开更多
(Quasi-)closed-form results for the statistical properties of unmanned aerial vehicle(UAV)airto-ground channels are derived for the first time using a novel spatial-vector-based method from a threedimensional(3-D)arbi...(Quasi-)closed-form results for the statistical properties of unmanned aerial vehicle(UAV)airto-ground channels are derived for the first time using a novel spatial-vector-based method from a threedimensional(3-D)arbitrary-elevation one-cylinder model.The derived results include a closed-form expression for the space-time correlation function and some quasi-closed-form ones for the space-Doppler power spectrum density,the level crossing rate,and the average fading duration,which are shown to be the generalizations of those previously obtained from the two-dimensional(2-D)one-ring model and the 3-D low-elevation one-cylinder model for terrestrial mobile-to-mobile channels.The close agreements between the theoretical results and the simulations as well as the measurements validate the utility of the derived channel statistics.Based on the derived expressions,the impacts of some parameters on the channel characteristics are investigated in an effective,efficient,and explicable way,which leads to a general guideline on the manual parameter estimation from the measurement description.展开更多
In GNSS-denied environments,signals of opportunity(SOP)offer an efficient and passive solution for navigation and positioning by utilizing ambient signals.Nevertheless,conventional SOP techniques face significant chal...In GNSS-denied environments,signals of opportunity(SOP)offer an efficient and passive solution for navigation and positioning by utilizing ambient signals.Nevertheless,conventional SOP techniques face significant challenges in real-time processing,especially under sub-Nyquist sampling conditions,due to high data acquisition rates and offgrid errors.To address this,this paper proposes the signal reconstruction and kernel sparse encoding(SRKSE)model,a novel general framework for high-precision parameter estimation.By combining compressed sensing with a deep unfolding network,the SRKSE model not only achieves robust signal reconstruction but also effectively reduces quantization errors.Key innovations of SRKSE include dual crossattention mechanisms for enhanced feature extraction,sinc sparse kernel encoding to minimize quantization errors,and a custom loss function for balanced optimization.With these advancements,SRKSE achieves up to a 650-fold improvement in time of arrival(TOA)estimation accuracy while operating at just 1%of the Nyquist sampling rate.The SRKSE surpasses both conventional and deep learning-based techniques in accuracy and efficiency,especially when operating under sub-Nyquist sampling conditions.Simulations and real-world experiments confirm the reliability and potential of SRKSE for real-time applications in IoT and wireless communication.展开更多
基金Natural Science Foundation of Inner Mongolia Autonomous Region of China(No.2013MS0916)Research Program of Science and Technology at Universities of Inner Mongolia Autonomous Region(No.NJZY237)
文摘With the appearance of novel radar signal with low intercept probability, the bandwidth of radar receiver is wider and wider. Wideband digital receiver becomes a research hotspot in the field of communication, radar and electronic reconnaissance, etc. As one of wideband digital receiver systems, digital channelized receiver has become a research emphasis due to the characteristics of full probability receiving and processing multiple signals. Digital channelized technology and signal sampling theory are deeply studied and an efficient channelized model is derived based on filter banks. The correctness of the model is verified by computer simulation The model has less computation compared with the traditional model, which is suitable for engineering application
文摘The data on the hillslope and channelized debris flows in the Shitou area of central Taiwan occurred during Typhoons Toraji and Nali in 2001 were applied in this paper. The geomorphic parameters, including the flow length, gully gradient, drainage area and form factor of the debris flows were determined by spatial analysis using a Geographic Information System (GIS) based on the data derived from field investigation, aerial photographs, and topographical maps. According to such determined geomorphic parameters, the threshold conditions and empirical equations, such as the relationship between the gully gradient and drainage area and that between gully length and drainage area and topographic parameter, are presented and used to distinguish the geomorphic characteristics between the channelized and hillslope debris flows.
文摘A novel efficient partial sharing channelization structure with odd and even stacking is designed and implemented. There are two special designs in the proposed structure. Firstly, by the intensive channel overlap design, for non-cooperative wideband signals, the proposed structure can achieve good parameter estimation accuracy and high probability of complete interception.Secondly, based on the partial sharing design developed in this paper, the computation burden of the proposed structure can be greatly reduced compared with the traditional directly implemented structures. Experiments and numerical simulations are conducted to evaluate the proposed structure, which shows its improvements over traditional methods in terms of field programmable gate arrays(FPGA) resource consumption and parameter estimation accuracy.
基金supported by the Program for New Century Excellent Talents in University(NCET-06-0921)
文摘An approach is proposed to realize a digital channelized receiver in the fractional Fourier domain （FRFD） for signal intercept applications. The presented architecture can be considered as a generalization of that in the traditional Fourier domain. Since the linear frequency modulation （LFM） signal has a good energy concentration in the FRFD, by choosing an appropriate fractional Fourier transform （FRFT） order, the presented architecture can concentrate the broadband LFM signal into only one sub-channel and that will prevent it from crossing several sub-channels. Thus the performance of the signal detection and parameter estimation after the sub-channel output will be improved significantly. The computational complexity is reduced enormously due to the implementation of the polyphase filter bank decomposition, thus the proposed architecture can be realized as efficiently as in the Fourier domain. The related simulation results are presented to verify the validity of the theories and methods involved in this paper.
基金supportedin part by Natural Science Foundation under grant No.91338108,91438206Co-innovation Laboratory of Aerospace Broadband Network Technology
文摘For digital channelized frequency division multiple access based satellite communication(SATCOM) systems,it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously under limited and non-linear high-power amplifier conditions.In this paper,different from the traditional link supportability designs aiming at minimizing the total transponder output power,a maximal sum Shannon capacity optimization objective is firstly raised subject to link supportability constraints.Furthermore,an efficient multilevel optimization(MO) algorithm is proposed to solve the considered optimization problem in the case of single link for each terminal.Moreover,in the case of multiple links for one terminal,an improved MO algorithm involving Golden section and discrete gradient searching procedures is proposed to optimize power allocation over all links.Finally,several numerical results are provided to demonstrate the effectiveness of our proposals.Comparison results show that,by the MO algorithm,not only all links' supportability can be guaranteed but also a larger sum capacity can be achieved with lower complexity.
文摘Assessing environmental flows （e-flows） for urban rivers is important for water resources planning and river protection, Many e-flow assessment methods have been established based on species＇ habitat pro- vision requirements and pollutant dilution requirements, To avoid flood risk, however, many urban rivers have been transformed into straight, trapezoidal-profiled concrete channels, leading to the disappearance of valuable species, With the construction of water pollution-control projects, pollutant inputs into rivers have been effectively controlled in some urban rivers, For these rivers, the e-flows determined by tradi- tional methods will be very small, and will consequently lead to a low priority being given to river pro- tection in future water resources allocation and management, To more effectively assess the e-flows of channelized urban rivers, we propose three e-flow degrees, according to longitudinal hydrological con- nectivity （high, medium, and low）, in addition to the pollutant dilution water requirement determined by the mass-balance equation, In the high connectivity scenario, the intent is for the e-flows to maintain flow velocity, which can ensure the self-purification of rivers and reduce algal blooms; in the medium connectivity scenario, the intent is for the e-flows to permanently maintain the longitudinal hydrological connectivity of rivers that are isolated into several ponds by means of weirs, in order to ensure the exchange of material, energy, and information in rivers; and in the low connectivity scenario, the intent is for the e-flows to intermittently connect isolated ponds every few days （which is designed to further reduce e-flows）, The proposed methods have been used in Shiwuli River, China, to demonstrate their effectiveness, The new methods can offer more precise and realistic e-flow results and can effectively direct the construction and management of e-flow supply projects,
基金supported by Korea Institute of Geoscience and Mineral Resources(Project No.GP2017-024)Ministry of Trade and Industry [Project No.NP2017-021(20172510102090)]funded by National Research Foundation of Korea(NRF)Grants(Nos.NRF-2017R1C1B5017767,NRF-2017K2A9A1A01092734)
文摘Most inverse reservoir modeling techniques require many forward simulations, and the posterior models cannot preserve geological features of prior models. This study proposes an iterative static modeling approach that utilizes dynamic data for rejecting an unsuitable training image(TI) among a set of TI candidates and for synthesizing history-matched pseudo-soft data. The proposed method is applied to two cases of channelized reservoirs, which have uncertainty in channel geometry such as direction, amplitude, and width. Distance-based clustering is applied to the initial models in total to select the qualified models efficiently. The mean of the qualified models is employed as a history-matched facies probability map in the next iteration of static models. Also, the most plausible TI is determined among TI candidates by rejecting other TIs during the iteration. The posterior models of the proposed method outperform updated models of ensemble Kalman filter(EnKF) and ensemble smoother(ES) because they describe the true facies connectivity with bimodal distribution and predict oil and water production with a reasonable range of uncertainty. In terms of simulation time, it requires 30 times of forward simulation in history matching, while the EnKF and ES need 9000 times and 200 times, respectively.
基金financial support from the Science and Technology Service Network Initiative Program of the Chinese Academy of Sciences (grant no.KFJ-EW-STS-094-2)"Hundred Talents" Program of the Chinese Academy of Sciences (Sulijun)+2 种基金the National Natural Science Foundation of China (grant no.41201012, 51208218)the Hundred Young Talents Program of the Institute of Mountain Hazards and Environment (grant no.SDSQB-2013-01)the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists (grant no.2012T1Z0042)
文摘Granular mass flows （e.g., debris flows/avalanches） in landslide-prone areas are of great concern because they often cause catastrophic disasters as a result of their long run-out distances and large impact forces. To investigate the factors influencing granular mass flow mobility, experimental tests were conducted in a flume model. Granular materials consisting of homogeneous sand and non- homogeneous sandy soil were used for studying particle size effects. Run-out tests with variable flow masses, water contents, and sloping channel confinement parameters were conducted as well. The results indicated that granular mass flow mobility was significantly influenced by the initial water content; a critical water content corresponding to the smallest flow mobility exists for different granular materials. An increase in the total flow mass generally induced a reduction in the travel angle （an increase in flow mobility）. Consistent with field observations, the travel angles for different granular materials decreased roughly in proportion to the logarithm of mass. The flume model tests illustrate that the measured travel angles increase as the proportion of fine particles increases. Interestingly, natural terrain possesses critical confinement characteristics for different granular mass flows.
文摘Riparian zones of channelized agricultural streams in northwestern Mississippi typically consist of narrow vegetative corridors low in habitat diversity and lacking riparian wetlands. Land clearing practices and stream channelization have led to the development of gully erosion and further fragmentation of these degraded riparian zones. Currently, installation of a gully erosion control structure (drop pipe) at the riparian zone-agricultural field interface leads to the incidental establishment of four riparian habitat types that differ in habitat area, vegetative structure, and pool size. Small mammals were sampled within four sites of each habitat type from June 1994 to July 1995. Small mammal diversity, abundance, and hispid cotton rat (Sigmodon hispidus) weight were the least within smallest Type I habitats with the least vegetative structural diversity and were the greatest within the larger Type II, III, or IV habitats having greater vegetative structural diversity and pool size. Small mammal diversity and abundance were the least in the summer 1994, increased in the fall 1994, and then declined later in our study. Hispid cotton rat abundance was the least in summer 1994, winter 1994, and spring 1995 and was the greatest in fall 1994 and summer 1995. Our results suggest that modifying the drop pipe installation design to facilitate the development of larger riparian habitats with greater vegetative structural diversity will provide the greatest benefits for small mammals.
文摘A structure of dynamic reconfigurable channelized filter bank is proposed in order to solve the problem that the uniform channelized receiver cannot receive the cross-channel and wideband signal. The dynamic reconfigurable channelized filter bank is divided into two parts-the analysis filter bank and the synthesis filter bank. The function of the analysis filter bank is to divide the received signal into several sub-signals according to the channel division. Then the sub-signals of each channel need to be detected and discriminated. At last, we use the sub-signals to reconstruct the original received signal by the synthesis filter bank. The analysis filter and the synthesis filter bank of the dynamic reconfigurable channelized filter bank are all efficient polyphase structures, so it can save more hardware resources and has extensive applicability. The structure is simulated by MATLAB and the simulation results verify the correctness of this structure.
文摘针对UAV在仿真实验中自动跟踪移动目标的需求,提出基于改进CSRT(channel and spatial reliability-aware tracker)算法的无人机长时自动跟踪方法。通过导向滤波加拉普拉斯算子LOGF(laplacian of guided filter)检测获取目标边缘特征,再与HOG(histogram of oriented gradient)和CN(color names)特征融合,增强算法对目标的判别能力;使用平均峰值相关能量和感知哈希汉明距离来综合判定目标状态,当判定目标被遮挡时,采用YOLOv8定位目标,再将定位结果传输至跟踪算法继续跟踪目标。仿真结果表明:在搭建的仿真环境中算法能够在目标被遮挡时仍能长时稳定的跟踪目标,为无人机目标跟踪算法研究提供了良好的仿真实验环境。
基金supported by the State key Laboratory of Hydroscience and Engineering of Tsinghua University(Grant Nos.Sklhse-2007-B-03,2011-KY-4)
文摘To enhance the efficiency of a pathogen forecasting model in the beach areas of southern Lake Michigan and to reduce the computation time, the near-shore current is approximated as a channelized flow parallel to the shorelines in clockwise or anti-clock- wise direction within the accuracy tolerance range. A channelized model with a curvilinear boundary can significantly reduce the computation effort, and at the same time achieve a good agreement between the predicted and measured water surface elevations, currents, and water temperatures. The sensitivity analysis results show that the suitable channel width for the near-shore region of southern Lake Michigan should be no less than 10 kin. The modeling results of the water temperature are much less sensitive to the channel width than those of the current velocity and the water surface elevation. The modeling results also show a close correlation between the speeds of the wind and the near-shore current. The current may fully respond the wind stress with a time lag of several hours. The correlation may provide an approximate estimation of the lake circulation under some wind conditions for a practical fore- casting purpose. More complex wind-current relationships need to be described with a more sophisticated hydrodynamic model. This verified model can be used for the pathogen forecasting in the near-shore regions of southern Lake Michigan in the future.
基金supported by the National Natural Science Foundation of China,Nos.82172196(to KX),82372507(to KX)the Natural Science Foundation of Hunan Province,China,No.2023JJ40804(to QZ)the Key Laboratory of Emergency and Trauma(Hainan Medical University)of the Ministry of Education,China,No.KLET-202210(to QZ)。
文摘Ischemia–reperfusion injury is a common pathophysiological mechanism in retinal degeneration.PANoptosis is a newly defined integral form of regulated cell death that combines the key features of pyroptosis,apoptosis,and necroptosis.Oligomerization of mitochondrial voltage-dependent anion channel 1 is an important pathological event in regulating cell death in retinal ischemia–reperfusion injury.However,its role in PANoptosis remains largely unknown.In this study,we demonstrated that voltage-dependent anion channel 1 oligomerization-mediated mitochondrial dysfunction was associated with PANoptosis in retinal ischemia–reperfusion injury.Inhibition of voltage-dependent anion channel 1 oligomerization suppressed mitochondrial dysfunction and PANoptosis in retinal cells subjected to ischemia–reperfusion injury.Mechanistically,mitochondria-derived reactive oxygen species played a central role in the voltagedependent anion channel 1-mediated regulation of PANoptosis by promoting PANoptosome assembly.Moreover,inhibiting voltage-dependent anion channel 1 oligomerization protected against PANoptosis in the retinas of rats subjected to ischemia–reperfusion injury.Overall,our findings reveal the critical role of voltage-dependent anion channel 1 oligomerization in regulating PANoptosis in retinal ischemia–reperfusion injury,highlighting voltage-dependent anion channel 1 as a promising therapeutic target.
文摘Lithium–sulfur(Li–S)batteries are promisingcandidates for next-generation energy storagegiven their high energy density and potential low cost.Chemically activated carbon(CAC)is often used fortheir cathodes,because it has a high specific surfacearea for sulfur loading.We have developed a pressurizedphysical activation(PPA)method that producedan activated carbon(PPAC)with a high specific surfacearea comparable to that of CAC.The pore structure of PPAC could be changed and its use as a cathode material for Li–Sbatteries was investigated.Battery tests at different capacity rates(C-rates)showed that it had a much improved high-rate performancewith a discharge capacity of 900 mAh/(g of sulfur)at 1 C,in contrast to only 600 mAh/(g of sulfur)for CAC.Porestructure analyses showed that PPAC prepared at a high activation temperature(1000℃)had unusual channel-like mesoporesbetween the microdomains that are the basic structural units of artificial carbon materials.These are connected to microporesdeveloped in each microdomain,and deliver ions from the surroundings to the internal pores and vice versa.The well-developedmicropores and mesopores of PPAC respectively ensured the high adsorption of lithium polysulfides and a high rate ofion diffusion.Compared to CAC,PPAC is a high-performance,low-cost cathode material that is promising for use in futureLi–S batteries.
基金National Natural Science Foundation of China(U24A2038)。
文摘The effects of channel segregation on the macro-and micro-scale chemical composition,microstructure,hardness,and tensile deformation behavior of Ti45Nb wires were investigated.The results show that wires with severe channel segregation exhibit a macroscopic chemical composition identical to those without segregation,and 3D X-ray imaging result also reveals no abnormalities.After annealing,both types of wires exhibit an equiaxed single-phase microstructure with comparable grain sizes,suggesting that channel segregation has negligible influence on the macroscopic composition and grain size.Metallographic examination reveals that channel segregation manifests as spot-like features in the transverse section and band-like structures in the longitudinal section.EDS analysis identifies these regions as Ti-enriched segregations,with a Ti content higher than that of the surrounding matrix by approximately 4.42wt%.Compared to segregation-free wires,those containing extensive channel segregation demonstrate a 15.5%increase in ultimate tensile strength and a 12.3%increase in yield strength,but suffer a reduction in elongation and reduction of area by 19.8%and 18.9%,respectively.Furthermore,the mechanical properties of wires with segregation show significant fluctuations.Fractographic analysis reveals a larger fracture surface area in segregated wires.Severe dislocation pile-ups occur at the interfaces of these segregated regions,initiating microcrack nucleation.This promotes rapid crack propagation of the Ti45Nb wire,leading to a significant decrease in plasticity and reduction of area.
基金Natural Science Foundation of Shaanxi Province (2023-JC-YB-312)。
文摘Ultrafine-grained(UFG)pure titanium was produced by equal channel angular pressing for 4 passes,followed by rotatory swaging at room temperature.The strain-controlled low-cycle fatigue tests of UFG and coarse-grained(CG)pure titanium were conducted by Instron electro-hydraulic servo fatigue testing machine in the strain amplitude range of 0.5%—1.1%at room temperature.Transmission electron microscope(TEM)and scanning electron microscope were used to investigate the microstructure and fracture surface of UFG pure titanium after fatigue tests.Results show that UFG pure titanium exhibits a longer low-cycle fatigue life,compared with the CG pure titanium.For example,at a total strain amplitude of 0.5%,UFG and CG pure titanium has fatigue life of 10850 and 4820 cycles,respectively.Significant cyclic softening occurs in UFG pure titanium,except in the case of a total strain amplitude of 0.5%.Hysteresis loop area is increased rapidly with the increase in strain amplitude.The fracture surface shows that the fatigue crack is initiated from the specimen surface.A series of fatigue striations and many microcracks exist in the propagation region.With the increase in strain amplitude,the predominant failure mode is transformed from ductile failure into quasi-cleavage failure.Dislocation slip is the main plastic deformation mechanism of UFG pure titanium during low-cycle fatigue deformation.
基金supported by ANID-FONDECYT 1200908(to JF),ANID-FONDECYT 1211082 and 1250856(to GEY)by the Millennium Nucleus for the Study of Pain NCN19_038(Mi Nu SPain)(to GEY)funded by the ANID scholarship 21201176。
文摘Numerous pathological states of the nervous system involve alterations in neuronal excitability and synaptic dysfunction,which depend on the function of ion channels.Due to their critical involvement in health and disease,the search for new compounds that modulate these proteins is still relevant.Traditional medicine has long been a rich source of neuroactive compounds.For example,the indigenous Mapuche people have used the leaves and bark of the Drimys winteri tree for centuries to treat various diseases.Consequently,several studies have investigated the biological effects of compounds in Drimys winteri,highlighting sesquiterpenes such asα-humulene,drimenin,polygodial,andα-,β-,γ-eudesmol.However,there is currently no literature review focusing on the ability of these sesquiterpenes to modulate ion channels.This review summarizes the current knowledge about neuroactive compounds found in Drimys winteri,with special emphasis on their direct actions on neuronal ion channels.Several Drimys winteri sesquiterpenes modulate a diverse array of neuronal ion channels,including transient receptor potential channels,gamma-aminobutyric acid A receptors,nicotinic acetylcholine receptors,and voltage-dependent Ca^(2+)and Na^(+)channels.Interestingly,the modulation of these molecular targets by Drimys winteri sesquiterpenes correlates with their therapeutic actions.The promiscuous pharmacological profile of Drimys winteri sesquiterpenes suggests they modulate multiple protein targets in vivo,making them potentially useful for treating complex,multifactorial diseases.Further studies at the molecular level may aid in developing multitargeted drugs with enhanced therapeutic effects.
基金supported by the Natural Science Foundation of Shandong Province under Grant ZR2024MF062the open research fund of National Mobile Communications Research Laboratory,Southeast University under Grants 2025D03+1 种基金the Future Plan Program for Young Scholars of Shandong University,and the Innovation and Technology Support Program for Young Scholars of Colleges and Universities in Shandong Province under Grant 2022KJ009The B6G R&D Group in Shandong University is greatly thanked for channel measurements.
文摘The smart meter communication system has substantial application value for the construction and upgrading of the entire power system.The deployment of the transmitter(Tx)of the smart meter system in the residential scenarios is vexed by the need for more theoretical support.This paper mainly studies the communication channel between the Tx at semibasement and receiver(Rx)at outdoor.The design of an effective communication system relies on an accurate understanding of channel characteristics.Channel measurements and ray-tracing channel modeling are conducted to obtain channel data.The influence of different positions at same semi-basement is studied.Typical channel characteristics are analyzed,such as power delay profile(PDP),power angular profile(PAP),root-mean-square(RMS)delay spread(DS),channel capacity,received power,and path loss.The influence of different semi-basement placements and different floor heights is also compared.Besides,the channel measurements and simulation data fit well,which can illustrate the validity and reliability of the acquired channel data.This paper can provide theoretical support for the design and optimization of smart meter communication systems in semi-basement scenarios.
基金supported in part by the National Key Research and Development Program of China(2021YFB2900501)in part by the Shaanxi Science and Technology Innovation Team(2023-CX-TD-03)+3 种基金in part by the Science and Technology Program of Shaanxi Province(2021GXLH-Z-038)in part by the Natural Science Foundation of Hunan Province(2023JJ40607 and 2023JJ50045)in part by the Scientific Research Foundation of Hunan Provincial Education Department(23B0713 and 24B0603)in part by the National Natural Science Foundation of China(62401371,62101275,and 62372070).
文摘(Quasi-)closed-form results for the statistical properties of unmanned aerial vehicle(UAV)airto-ground channels are derived for the first time using a novel spatial-vector-based method from a threedimensional(3-D)arbitrary-elevation one-cylinder model.The derived results include a closed-form expression for the space-time correlation function and some quasi-closed-form ones for the space-Doppler power spectrum density,the level crossing rate,and the average fading duration,which are shown to be the generalizations of those previously obtained from the two-dimensional(2-D)one-ring model and the 3-D low-elevation one-cylinder model for terrestrial mobile-to-mobile channels.The close agreements between the theoretical results and the simulations as well as the measurements validate the utility of the derived channel statistics.Based on the derived expressions,the impacts of some parameters on the channel characteristics are investigated in an effective,efficient,and explicable way,which leads to a general guideline on the manual parameter estimation from the measurement description.
基金National Key Laboratory of Unmanned Aerial Vehicle Technology(No.202408)Key Laboratory of Smart Earth(No.KF2023ZD01-05)。
文摘In GNSS-denied environments,signals of opportunity(SOP)offer an efficient and passive solution for navigation and positioning by utilizing ambient signals.Nevertheless,conventional SOP techniques face significant challenges in real-time processing,especially under sub-Nyquist sampling conditions,due to high data acquisition rates and offgrid errors.To address this,this paper proposes the signal reconstruction and kernel sparse encoding(SRKSE)model,a novel general framework for high-precision parameter estimation.By combining compressed sensing with a deep unfolding network,the SRKSE model not only achieves robust signal reconstruction but also effectively reduces quantization errors.Key innovations of SRKSE include dual crossattention mechanisms for enhanced feature extraction,sinc sparse kernel encoding to minimize quantization errors,and a custom loss function for balanced optimization.With these advancements,SRKSE achieves up to a 650-fold improvement in time of arrival(TOA)estimation accuracy while operating at just 1%of the Nyquist sampling rate.The SRKSE surpasses both conventional and deep learning-based techniques in accuracy and efficiency,especially when operating under sub-Nyquist sampling conditions.Simulations and real-world experiments confirm the reliability and potential of SRKSE for real-time applications in IoT and wireless communication.
