基于局部密度聚类的WSN多Sink节点部署研究

针对无线传感器网络中传感器节点能量受限,网络生命周期短的问题,在考虑网络成本的情况下,提出一种基于节点局部密度聚类的多Sink节点优化部署算法。首先,基于多属性因子构建聚类决策函数确定Sink节点部署位置,完成传感器节点聚类;然后,根据下一跳节点与Sink节点间距离最短准则搜索并形成数据传输路径;最后,以网络生命周期成本比最大化为依据确定最优的Sink节点数目,实现多Sink节点优化部署。仿真结果表明:与已有算法相比,所提算法能够有效延长网络生命周期,具有较高的网络生命周期能效比。

跳数受限下的传感云网络多Sink节点重选址方法

当传感云网络中的Sink节点处于静止状态时,分布在其周围的邻居节点极易出现“能量空洞”,导致能量消耗不均,节点出现不同的网络生存期,影响节点间数据正常传输。为此,在限制节点跳数的前提下,提出一种多Sink节点重选址方法。基于Sink节点寿命和传感云网络代价函数引入质心理论,建立质点系并确定质心位置;将Sink节点向流量大的节点移动,并与其他Sink节点相互协作、避免发生冲突,直至到达质心位置,实现多Sink节点重选址。结果表明,所提方法重选址的节点生存时间最高为1 000 s为,数据包交付率为98%,节点平均剩余能量值高于0.6 J。

Dynamics and vibration reduction performance of asymmetric tristable nonlinear energy sink

With its complex nonlinear dynamic behavior,the tristable system has shown excellent performance in areas such as energy harvesting and vibration suppression,and has attracted a lot of attention.In this paper,an asymmetric tristable design is proposed to improve the vibration suppression efficiency of nonlinear energy sinks(NESs)for the first time.The proposed asymmetric tristable NES(ATNES)is composed of a pair of oblique springs and a vertical spring.Then,the three stable states,symmetric and asymmetric,can be achieved by the adjustment of the distance and stiffness asymmetry of the oblique springs.The governing equations of a linear oscillator(LO)coupled with the ATNES are derived.The approximate analytical solution to the coupled system is obtained by the harmonic balance method(HBM)and verified numerically.The vibration suppression efficiency of three types of ATNES is compared.The results show that the asymmetric design can improve the efficiency of vibration reduction through comparing the chaotic motion of the NES oscillator between asymmetric steady states.In addition,compared with the symmetrical tristable NES(TNES),the ATNES can effectively control smaller structural vibrations.In other words,the ATNES can effectively solve the threshold problem of TNES failure to weak excitation.Therefore,this paper reveals the vibration reduction mechanism of the ATNES,and provides a pathway to expand the effective excitation amplitude range of the NES.

A vertical track nonlinear energy sink

Eliminating the effects of gravity and designing nonlinear energy sinks(NESs)that suppress vibration in the vertical direction is a challenging task with numerous damping requirements.In this paper,the dynamic design of a vertical track nonlinear energy sink(VTNES)with zero linear stiffness in the vertical direction is proposed and realized for the first time.The motion differential equations of the VTNES coupled with a linear oscillator(LO)are established.With the strong nonlinearity considered of the VTNES,the steady-state response of the system is analyzed with the harmonic balance method(HBM),and the accuracy of the HBM is verified numerically.On this basis,the VTNES prototype is manufactured,and its nonlinear stiffness is identified.The damping effect and dynamic characteristics of the VTNES are studied theoretically and experimentally.The results show that the VTNES has better damping effects when strong modulation responses(SMRs)occur.Moreover,even for small-amplitude vibration,the VTNES also has a good vibration suppression effect.To sum up,in order to suppress the vertical vibration,an NES is designed and developed,which can suppress the vertical vibration within certain ranges of the resonance frequency and the vibration intensity.

海洋牧场WSN中移动Sink节点的路径规划

针对静态部署的海洋牧场无线传感网络在数据多跳传输过程中近Sink节点区域易出现能量空洞的问题,提出一种基于改进蚁群算法的移动Sink节点可靠通信路径规划方法。首先,对于传统蚁群算法,采用非均匀分配初始信息素浓度,解决算法初期盲目搜索的问题;修改状态转移概率函数,增加拥挤度因子,避免死锁现象的同时加快收敛速度;采用改进的信息素更新规则,保证算法后期的收敛能力。其次,利用LEACH协议对网络进行分簇,根据簇头节点的位置和通信覆盖区情况,构建移动Sink遍历节点集。最后,将移动Sink节点路径规划问题看成旅行商问题,并通过改进蚁群算法和构建的骨干节点集求出移动Sink节点的最优路径。仿真实验结果表明,在275个网络节点规模内,该方法与其他算法相比,在路径长度方面依次减少了41.9%、20.3%、30.4%,数据传输时延依次降低了42%、38.5%、46.7%,网络吞吐量依次提高了10%、10.6%、16.4%,验证了该方法的优越性。文章所提出的方法通过引入移动Sink节点并利用其移动路径的合理性可以有效优化海洋牧场无线传感网络数据接收的可靠性、网络的能耗特性与生命周期。

Dynamic performance and parameter optimization of a half-vehicle system coupled with an inerter-based X-structure nonlinear energy sink

Inspired by the demand of improving the riding comfort and meeting the lightweight design of the vehicle, an inerter-based X-structure nonlinear energy sink(IXNES) is proposed and applied in the half-vehicle system to enhance the dynamic performance. The X-structure is used as a mechanism to realize the nonlinear stiffness characteristic of the NES, which can realize the flexibility, adjustability, high efficiency, and easy operation of nonlinear stiffness, and is convenient to apply in the vehicle suspension, and the inerter is applied to replacing the mass of the NES based on the mass amplification characteristic. The dynamic model of the half-vehicle system coupled with the IX-NES is established with the Lagrange theory, and the harmonic balance method(HBM) and the pseudo-arc-length method(PALM) are used to obtain the dynamic response under road harmonic excitation. The corresponding dynamic performance under road harmonic and random excitation is evaluated by six performance indices, and compared with that of the original half-vehicle system to show the benefits of the IX-NES. Furthermore, the structural parameters of the IX-NES are optimized with the genetic algorithm. The results show that for road harmonic and random excitation, using the IX-NES can greatly reduce the resonance peaks and root mean square(RMS) values of the front and rear suspension deflections and the front and rear dynamic tire loads, while the resonance peaks and RMS values of the vehicle body vertical and pitching accelerations are slightly larger.When the structural parameters of the IX-NES are optimized, the vehicle body vertical and pitching accelerations of the half-vehicle system could reduce by 2.41% and 1.16%,respectively, and the other dynamic performance indices are within the reasonable ranges.Thus, the IX-NES combines the advantages of the inerter, X-structure, and NES, which improves the dynamic performance of the half-vehicle system and provides an effective option for vibration attenuation in the vehicle engineering.

A viscoelastic nonlinear energy sink with an electromagnetic energy harvester:Narrow-band random response

Nonlinear energy sink is a passive energy absorption device that surpasses linear dampers, and has gained significant attention in various fields of vibration suppression. This is owing to its capacity to offer high vibration attenuation and robustness across a wide frequency spectrum. Energy harvester is a device employed to convert kinetic energy into usable electric energy. In this paper, we propose an electromagnetic energy harvester enhanced viscoelastic nonlinear energy sink(VNES) to achieve passive vibration suppression and energy harvesting simultaneously. A critical departure from prior studies is the investigation of the stochastic P-bifurcation of the electromechanically coupled VNES system under narrowband random excitation. Initially, approximate analytical solutions are derived using a combination of a multiple-scale method and a perturbation approach. The substantial agreement between theoretical analysis solutions and numerical solutions obtained from Monte Carlo simulation underscores the method's high degree of validity. Furthermore, the effects of system parameters on system responses are carefully examined. Additionally, we demonstrate that stochastic P-bifurcation can be induced by system parameters, which is further verified by the steady-state density functions of displacement. Lastly,we analyze the impacts of various parameters on the mean square current and the mean output power, which are crucial for selecting suitable parameters to enhance the energy harvesting performance.

Effects of urbanization and forest type on species composition and diversity,forest characteristics,biomass carbon sink,and their associations in Changchun,Northeast China:implications for urban carbon stock improvement

Differences in forest attributes and carbon sequestration of each organ and layer between broadleaved and conifer forests of central and outer urban areas are not well-defined,hindering the precise management of urban forests and improvement of function.To clarify the effect of two forest types with different urbanization intensities,we determined differences in vegetation composition and diversity,structural traits,and carbon stocks of 152 plots(20 m×20 m)in urban park forests in Changchun,which had the largest green quantity and carbon density effectiveness.We found that 1.1-fold thicker and healthier trees,and 1.6-to 2.0-fold higher,healthier,denser,and more various shrubs but with sparser trees and herbs occurred in the central urban forests(p<0.05)than in the outer forests.The conifer forests exhibited 30–70%obviously higher tree aboveground carbon sequestration(including stem and leaf)and 20%bigger trees,especially in the outer forests(p<0.05).In contrast,1.1-to 1.5-fold higher branch stocks,healthier and more diverse trees were found in broadleaved forests of both the inner and outer forests(p<0.05).Plant size and dominant species had similarly important roles in carbon stock improvement,especially big-sized woody plants and Pinus tabuliformis.In addition,a higher number of deciduous or needle species positively affected the broadleaved forest of the central urban area and conifer forest of the outer urban area,respectively.These findings can be used to guide precise management and accelerate the improvement of urban carbon function in Northeast China in the future.

Effects of phosphorus limitation on sinking velocities of phytoplankton during summer in the Changjiang River Estuary

The sinking of phytoplankton is critical to organic matter transportation in the ocean and it is an essential process for the formation of coastal hypoxic zones.This study was based on a field investigation conducted during the summer of 2022 in the Changjiang River(Yangtze River) Estuary(CJE) and its adjacent waters.The settling column method was employed to measure the sinking velocity(SV) of different size fractions of phytoplankton at the surface of the sea and to analyze their environmental control mechanisms.The findings reveal significant spatial variation in phytoplankton SV(-0.55-2.41 m/d) within the CJE.High-speed sinking was predominantly observed in phosphate-depleted regions beyond the CJE front.At the same time,an upward trend was more commonly observed in the phosphate-rich regions near the CJE mouth.The SV ranges for different sizefractionated phytoplankton,including micro-(>20 μm),nano-(2-20 μm),and picophytoplankton(0.7-2 μm),were-0.50-4.74 m/d,-1.04-1.59 m/d,and-1.24-1.65 m/d,respectively.Correlation analysis revealed a significant negative correlation between SV and dissolved inorganic phosphorus(DIP),implying that the influence of DIP contributes to SV.The variations in phytoplankton alkaline phosphatase activity suggested a significant increase in SV across all size fractions in the event of phosphorus limitation.Phytoplankton communities with limited photo synthetic capacity(maximum photochemical efficience,Fv/Fm <0.3) were found to have higher SV than that of communities with strong capacity,suggesting a link between sinking and alterations in physiological conditions due to phosphate depletion.The findings from the in situ phosphate enrichment experiments confirmed a marked decrease in SV following phosphate supplementation.These findings suggest that phosphorus limitation is the primary driver of elevated SV in the CJE.This study enhances the comprehension of the potential mechanisms underlying hypoxic zone formation in the CJE,providing novel insights into how nearshore eutrophication influences organic carbon migration.

Effects of nutrient limitations on the sinking velocity of Thalassiosira weissflogii

The sinking of diatoms is critic al to the formation of oceanic biological pumps and coastal hypoxic zones.However,little is known about the effects of different nutrient restrictions on diatom sinking.In this study,we measured the sinking velocity(SV) of Thalassiosira weissflogii using a new phytoplankton video observation instrument and analyzed major biochemical components under varying nutrient conditions.Our results showed that the SV of T.weissflogii under different nutrient limitation conditions varied substantially.The highest SV of(1.77±0.02) m/d was obtained under nitrate limitation,signific antly surpassing that under phosphate limitation at(0.98±0.13) m/d.As the nutrient limitation was released,the SV steadily decreased to(0.32±0.03) m/d and(0.15±0.05) m/d,respectively.Notably;under conditions with limited nitrate and phosphate concentrations,the SV values of T.weissflogii significantly positively correlated with the lipid content(P <0.001),with R^(2) values of 0.86 and 0.69,respectively.The change of the phytoplankton SV was primarily related to the intracellular compo sition,which is controlled by nutrient conditions but did not significantly correlate with transparent extracellular polymer and biosilica contents.The results of this study help to understand the regulation of the vertical sinking process of diatoms by nutrient restriction and provide new insights into phytoplankton dynamics and their relationship with the marine nutrient structure.

A comprehensive review on microchannel heat sinks for electronics cooling

The heat generation of electronic devices is increasing dramatically,which causes a serious bottleneck in the thermal management of electronics,and overheating will result in performance deterioration and even device damage.With the development of micro-machining technologies,the microchannel heat sink(MCHS)has become one of the best ways to remove the considerable amount of heat generated by high-power electronics.It has the advantages of large specific surface area,small size,coolant saving and high heat transfer coefficient.This paper comprehensively takes an overview of the research progress in MCHSs and generalizes the hotspots and bottlenecks of this area.The heat transfer mechanisms and performances of different channel structures,coolants,channel materials and some other influencing factors are reviewed.Additionally,this paper classifies the heat transfer enhancement technology and reviews the related studies on both the single-phase and phase-change flow and heat transfer.The comprehensive review is expected to provide a theoretical reference and technical guidance for further research and application of MCHSs in the future.

Heat dissipation enhancement method for finned heat sink for AGV motor driver's IGBT module

With the widespread use of high-power and highly integrated insulated gate bipolar transistor(IGBT),their cooling methods have become challenging.This paper proposes a liquid cooling scheme for heavy-duty automated guided vehicle(AGV)motor driver in port environment,and improves heat dissipation by analyzing and optimizing the core component of finned heat sink.Firstly,the temperature distribution of the initial scheme is studied by using Fluent software,and the heat transfer characteristics of the finned heat sink are obtained through numerical analysis.Secondly,an orthogonal test is designed and combined with the response surface methodology to optimize the structural parameters of the finned heat sink,resulting in a 14.57%increase in the heat dissipation effect.Finally,the effectiveness of heat dissipation enhancement is verified.This work provides valuable insights into improving the heat dissipation of IGBT modules and heat sinks,and provides guidance for their future applications.

Optimizing Heat Sink Performance by Replacing Fins from Solid to Porous inside Various Enclosures Filled with a Hybrid Nanofluid

The current study generally aims to improve heat transfer in heat sinks by presenting a numerical analysis of natural convection of an enclosure with hot right and cool left walls,and thermally insulated top and bottom walls.The cold wall included configurations(half circle/half square)in various sizes(S=0.1,0.2,and 0.3),numbers(N=1,2,3,and 4),and locations(C=0.35,and 0.65).A heat sink is constructed of Aluminum attached to the hot wall,and composed of five fins with protrusions.Fins of the heat sink will be examined in a solid and porous structure.The enclosure is filled with a hybrid nanofluid of Nanoparticles(MWCNT and Fe3O4)and water.The current study utilized COMSOL Multiphysics software due to its efficacy in addressing scientific and technical challenges involving partial differential equations.The solving of the governing equations is achieved using the finite element method with various parameters:Rayleigh number(Ra=10^(3)–10^(6)),Darcy number(Da=10^(-2),10^(-3)),solid volume fraction(ϕ=0–0.06)to determine stream function,isotherms lines,and average Nusselt number(Nu).The results of numerical simulations show that heat sink with solid fins have a 97%higher stream function when Ra is raised from 10^(3) to 105.Whilst with porous fin heat sink,a stream function 96%for Da=10^(-3) and 94%for Da=10^(-2).Changing solid fins to porous increases stream functions by 9%at Da=10^(-3) and 20%at Da=10^(-2).It has been found that Ra increases Nu by 44%for solid fins and 50%for porous fins.Making solid fins porous increases Nu by 54%at Ra=10^(6).The high increase in the percentage of(Nu)indicates the importance of the improvement in heat transfer,and this distinguishes the results of the current study from previous studies.Nu values were found highest for(half square)compared to(half circle),with 2%increases for numbers,11.6%for sizes,and 11%for location.Solid volume fractions for all Ra at a solid-finned heat sink increased Nu by 23%.

Carbon emission risk of construction industry in Hebei Province of China based on carbon sink thresholds

In order to assess the environmental risks caused by carbon emissions from the construction industry in Hebei Province of China,an environmental risk assessment model based on forest carbon sink threshold was constructed to evaluate the carbon emission risks of the construction industry in Hebei Province,China from 2005 to 2020.The results are shown as follows:(1)The overall carbon emissions of the construction industry in Hebei Province of China showed an inverted"V"-shaped evolution trend during the past 16 years.Tangshan and Shijiazhuang maintained high carbon emissions,while Langfang,Hengshui and Baoding saw rapid increases in carbon emissions.(2)The environmental safety threshold of carbon emission from the construction industry in Hebei Province,China,has been continuously improved,and the provincial environmental safety threshold is between 9475080-23144760 tons;The environmental safety threshold was the highest in Baoding and Langfang,and the lowest in Xingtai.(3)In the past 16 years,the carbon emission risk of the construction industry in Hebei Province of China has been in a state of extremely serious risk,and the risk index generally presents an inverted"V"type trend.(4)The carbon emission risk of Hebei city in China presents a spatial pattern of"high in the south and low in the north",which goes through two stages:risk increase period and risk reduction period.

Coupling and Long-term Change Characteristics of Forest Carbon Sink and Forestry Economic Development in China

[Objectives]To analyze the changes in of forest carbon sink and forestry economic development,provide reference for relevant management decisions,ecological governance and resource and environment management,and promote the development of green low-carbon economy in China.[Methods]Based on the data of six forest resource inventories from 1989 to 2018 and related studies,the comprehensive evaluation model of forest carbon sink and forestry economic development,the coupling degree model of forest carbon sink and forestry economic development,and the coupling coordination degree model of forest carbon sink and forestry economic development were adopted.The coupling degree of forest carbon sink and forestry economic development from 1992 to 2018 was analyzed.Stepwise regression and ARIMA model were used to analyze the influencing factors and lagging characteristics of forest carbon sink.The coupling degree between forest carbon sink and forestry economic development in China from 2019 to 2030 was predicted by autoregression and ADF test.The coupling between forest carbon sink and forestry economic development in China and its long-term change characteristics were also discussed in this study.[Results](i)The investment of ecological construction and protection,the actual investment of forestry key ecological projects,GDP and the import of forest products had a significant impact on forest resources carbon stock.The total output value of forestry industry,the actually completed investment of forestry key ecological projects and the export volume of forest products had a significant impact on the forest carbon sink,and the actually completed investment of forestry key ecological projects has the greatest impact on the two.(ii)The impact of actually completed investment of forestry key ecological projects had a lag of 2 years on the forest resources carbon stock and a lag of 1 year on the forest carbon sink.When investing in forest carbon sink,it is necessary to make a good plan in advance,and do a good job in forest resources management and time optimization.(iii)From 1992 to 2018,the coupling degree of forest resources carbon stock,forest carbon sink and long-term development of forestry economy in China was gradually increasing.Although there were some fluctuations in the middle time,the coupling degree of forest resources carbon stock and the long-term development of forestry economy increased by 9.24%annually,and the degree of coupling coordination increased from"serious imbalance"in 1992 to"high-quality coordination"in 2018.From 1993 to 2018,the coupling degree of forest carbon sink and long-term development of forestry economy increased by 9.63%annually,slightly faster than the coupling coordination degree of forest resources carbon stock and long-term development of forestry economy.The coordination level also rose from level 2 in 1993 to level 10 in 2018.(iv)The prediction shows that the coupling coordination degree of forest resources carbon stock,forest carbon sink and the long-term development of forestry economy would increase from 2019 to 2030.The coupling coordination degree(D)values of both were close to 1,the coordination level was also 10 for a long time,and the degree of coupling coordination was also maintained at the"high-quality coordination"level for a long time.[Conclusions]Forest has multiple benefits of society,economy and ecology,and forest carbon sink is only a benefit output.The long-term coupling analysis of forest carbon sink and forestry economic development is a key point to multiple benefit analysis.The analysis shows that the spillover effect and co-evolution effect of forest carbon sink in China are significant.From 1992 to 2018,the coupling coordination degree of forest carbon sink and forestry economic development was gradually rising.The prediction analysis also indicate that the coupling coordination degree between the forest carbon sink and the long-term development of forestry economy will remain at the level of"high-quality coordination"for a long time from 2019 to 2030.Therefore,improving the level of forest management and maintaining the current trend of increasing forest resources are the key to achieving the goal of carbon peaking and carbon neutrality in China.

基于随机移动模型的移动sinks无线移动传感器网络性能分析与改进

引入移动sinks节点是解决网络连通性、能耗平衡、提高网络生命周期和网络容量的有效方法。针对移动sinks节点的移动机制直接与网络性能相关,结合mWSNs体系结构,分析了基于随机移动模型的网络性能,提出了零数据包分片率的随机移动模型。理论分析与仿真结果表明,该模型能够保证数据零分片,提高了网络的时延性能和数据包传输成功率。

移动sinks无线移动传感器网络时延性能分析

结合mWSNs体系结构,分析了移动sinks无线传感器网络的时延组成和时延特性,并通过仿真实验分析了移动性对时延的影响。该分析结果既能用于mWSNs时延系统性能评价,又可为mWSNs系统参数(如移动sinks数量、速度、传输半径及数据包长度等)优化提供理论依据。同时,时延性能要与能量消耗综合考虑。

大规模传感网移动多Sink生物超启发式路径规划

大规模无线传感器网络节点数量多、部署范围广、数据传输时延长。针对上述问题,提出移动多Sink生物超启发式路径规划算法,采用蚁群优化作上层算子,根据网络运行过程中的变化,即节点数量和能量变化,实时优选下层算子集,选中的下层算子集规划各移动Sink节点的路径。仿真研究表明,所提算法有效解决多Sink节点的路径规划问题,减小网络时延。

Grain Sink Strength Related to Carbon Staying in the Leaves of Hybrid Wheat XN901

XN901 is a K-type three-line hybrid wheat with a high yield potential, and its leaves and stem remaining green during grain maturation, suggesting much assimilate stay in leaves and stem. The grain water content, grain volume, carbohydrate content, and enzyme activity of sucose metabolism in the grain, as well as source-sink relationship were studied in order to investigate the physiological reason of the assimilate remaining in leaves and stem at the late stage. The results showed that the hybrid grains had more water and soluble sugar, higher activities of acid invertase and sucrose synthase at the early stage that led to a faster expansion growth, greater grain volume and faster starch synthesis at the early to mid stage of grain development. Also it had a longer period for actively filling. As a result, the grain weight and yield of the hybrid were increased by 14 and 15% respectively compared to that of Shaan 229. Additionally, the biomass of XN901 was 41.7% more than that of control, but its harvest index was 9% lower than Shaan 229. However, its lower activity of sucrose synthase indicated a lower sink activity at the late stage, resulting in a slow rate of filling and starch synthesis. Also, the hybrid wheat XN901 had a large source-sink ratio. It is the main reason for much assimilate remaining in the straw at the late stage and lower harvest index. Strengthening the sink activity and raising the harvest index should be the key means of improving the yield of hybrid wheat.

基于移动sink节点的路由协议的比较与分析

设计基于移动sink节点的路由协议是移动sink无线传感网络中的一个关键问题。首先分析移动sink无线传感器网络的网络结构以及移动sink路由协议的评价指标。其次,对现有的移动sink路由协议进行归纳和总结,并将其分为非分层路由协议、基于虚拟网格的路由协议和基于虚拟簇的路由协议3类。最后,从网络总能耗、节点存活数以及基站接收到的数据包方面对其进行仿真,仿真结果进一步验证了理论上的分析,为选择有效的移动sink路由协议提供依据。