A Lane Change Model Considering the Stability of Cooperative Adaptive Cruise Control Platoon Fleet

In this article,lane change models for mixed traffic flow under cooperative adaptive cruise control(CACC)platoon formation are established.The analysis begins by examining the impact of lane changes on traffic flow stability.The influences of various factors such as lane change locations,timing,and the current traffic state on stability are discussed.In this analysis,it is assumed that the lane change location and the entry position in the adjacent lane have already been selected,without considering the specific intention behind the lane change.The speeds of the involved vehicles are adjusted based on an existing lane change model,and various conditions are analyzed for traffic flow disturbances,including duration,shock amplitude,and driving delays.Numerical calculations are provided to illustrate these effects.Additionally,traffic flow stability is factored into the lane change decision-making process.By incorporating disturbances to the fleet into the lane change income model,both a lane change intention model and a lane change execution model are constructed.These models are then compared with a model that does not account for stability,leading to the corresponding conclusions.

Emerging low-density polyethylene/paraffin wax/aluminum composite as a form-stable phase change thermal interface material

Thermal interface materials(TIMs) play a vital role in the thermal management of electronic devices and can significantly reduce thermal contact resistance(TCR). The TCR between the solid–liquid contact surface is much smaller than that of the solid–solid contact surface, but conventional solid–liquid phase change materials are likely to cause serious leakage. Therefore, this work has prepared a new formstable phase change thermal interface material. Through the melt blending of paraffin wax(PW) and low-density polyethylene(LDPE), the stability is improved and it has an excellent coating effect on PW. The addition of aluminum(Al) powder improves the low thermal conductivity of PW/LDPE, and the addition of 15wt% Al powder improves the thermal conductivity of the internal structure of the matrix by 67%. In addition, the influence of the addition of Al powder on the internal structure, thermal properties, and phase change behavior of the PW/LDPE matrix was systematically studied. The results confirmed that the addition of Al powder improved the thermal conductivity of the material without a significant impact on other properties, and the thermal conductivity increased with the increase of Al addition. Therefore, morphologically stable PW/LDPE/Al is an important development direction for TIMs.

Heterogeneity and non-linearity of ecosystem responses to climate change in the Qilian Mountains National Park, China

Ecosystem responses to climate change,particularly in arid environments,is an understudied topic.This study conducted a spatial analysis of ecosystem responses to short-term variability in temperature,precipitation,and solar radiation in the Qilian Mountains National Park,an arid mountainous region in Northwest China.We collected precipitation and temperature data from the National Science and Technology Infrastructure Platform,solar radiation data from the China Meteorological Forcing Dataset,and vegetation cover remote-sensing data from the Moderate Resolution Imaging Spectroradiometer.We used the vegetation sensitivity index to identify areas sensitive to climate change and to determine which climatic factors were significant in this regard.The findings revealed a high degree of heterogeneity and non-linearity of ecosystem responses to climate change.Four types of heterogeneity were identified:longitude,altitude,ecosystem,and climate disturbance.Furthermore,the characteristics of nonlinear ecosystem responses to climate change included:(1)inconsistency in the controlling climatic factors for the same ecosystems in different geographical settings;(2)the interaction between different climatic factors results in varying weights that affect ecosystem stability and makes them difficult to determine;and(3)the hysteresis effect of vegetation increases the uncertainty of ecosystem responses to climate change.The findings are significant because they highlight the complexity of ecosystem responses to climate change.Furthermore,the identification of areas that are particularly sensitive to climate change and the influencing factors has important implications for predicting and managing the impacts of climate change on ecosystems,which can help protect the stability of ecosystems in the Qilian Mountains National Park.

Demographic changes in China’s forests from 1998 to 2018

Background: Tree demography is an essential indicator of various forest ecosystem services, and understanding its changes is critical for the sustainable management of forests. During the past four decades, China implemented unprecedented forest restoration projects, which altered tree demography by increasing the number of trees and introducing new species. However, it remains unclear how species composition has changed in China in response to the past forest restoration and demographical processes.Methods: We applied Forest Stability Index(FSI) and the relative change of FSI(%FSI) to describe the population dynamics of tree species and structure in China since 1998, using field-survey data collected from over 200,000plot-records from the 6th to 9th National Forest Inventories(NFIs).Results: The overall populations of both natural and planted forests have grown rapidly from 1998 to 2018, while the range of changes in the relative tree density was more variable for natural forests(ranging from-8.53% to42.46%) than for planted forests(ranging from-1.01% to 13.31%). The populations declined only in some of the tree species, including Betula platyphylla, Ulmus pumila, and Robinia pseudoacacia. In contrast, the populations of trees in the largest size-class either remained stable or expanded.Conclusions: Tree density of China?s forests(both natural and planted forests) generally expanded and the overall populations increased in most size classes, with greater increases occurred in planted forests. In contrasting to the global decline trends of large diameter trees, here we found no apparent decline for trees in the largest size-class in China, highlighting China?s success in improving forest health and forest adaptations to climate change. We advocate for more studies to reveal the mechanisms of the changes in tree demography, which will help to improve forest ecosystem services such as the carbon sequestration capacity.

Experimental study on thermal and mechanical properties of tailings-based cemented paste backfill with CaCl_(2)·6H_(2)O/expanded vermiculite shape stabilized phase change materials

CaCl_(2)·6H_(2)O/expanded vermiculite shape stabilized phase change materials(CEV)was prepared by atmospheric impregnation method.Using gold mine tailings as aggregate of cemented paste backfill(CPB)material,the CPB with CEV added was prepared,and the specific heat capacity,thermal conductivity,and uniaxial compressive strength(UCS)of CPB with different cement-tailing ratios and CEV addition ratios were tested,the influence of the above variables on the thermal and mechanical properties of CPB was analyzed.The results show that the maximum encapsulation capacity of expanded vermiculite for CaCl_(2)·6H_(2)O is about 60%,and the melting and solidification enthalpies of CEV can reach 98.87 J/g and 97.56 J/g,respectively.For the CPB without CEV,the specific heat capacity,thermal conductivity,and UCS decrease with the decrease of cement-tailing ratio.For the CPB with CEV added,with the increase of CEV addition ratio,the specific heat capacity increases significantly,and the sensible heat storage capacity and latent heat storage capacity can be increased by at least 10.74%and 218.97%respectively after adding 12%CEV.However,the addition of CEV leads to the increase of pores,and the thermal conductivity and UCS both decrease with the increase of CEV addition.When cement-tailing ratio is 1:8 and 6%,9%,and 12%of CEV are added,the 28-days UCS of CPB is less than 1 MPa.Considering the heat storage capacity and cost price of backfill,the recommended proportion scheme of CPB material presents cement-tailing ratio of 1:6 and 12%CEV,and the most recommended heat storage/release temperature cycle range of CPB with added CEV is from 20 to 40℃.This work can provide theoretical basis for the utilization of heat storage backfill in green mines.

社会变迁中心理与行为的稳定性: 以谦虚效应为例

面对百年未有之大变局及生活质量生活方式的剧烈变迁,人们的心理行为乃至文化会如何变异?作者假设尽管社会变迁会影响和改变人类的某些心理和行为,但有些心理行为,因其受深层文化影响,会十分稳定,不受社会变迁的影响。近30年的有关谦虚效应的跨文化研究为这一假设提供了佐证。谦虚是中国传统文化深层结构中的集体主义的产物,这种跨文化差异本质上来源于东西方文化中个人主义与集体主义的差异。总结谦虚效应的30年系列研究结果表明尽管中国的经济社会发生了前所未有的发展,这个跨文化效应基本不变,说明源于深层文化的心理和行为存在高度的稳定性。

硅藻土基定形相变材料的制备及应用进展

硅藻土是硅藻植物经过漫长的沉积成岩而形成的一种非金属矿物。硅藻土具有丰富微孔、耐高温、耐腐蚀性、价格低廉和资源丰富等优点,作为一种良好的吸附载体材料而受到广泛关注。介绍了硅藻土的结构特点并归纳了硅藻土常见的几种改性方法,综述了硅藻土基定形相变材料的种类及制备方法,总结了该材料在建筑领域的应用进展,分析了现阶段硅藻土基定形相变材料研究中存在的问题,并提出未来工作中需要关注的重点,以期为其规模化推广应用提供参考。

碳纳米管和纳米铜导热粒子的热调节性能研究

采用原位聚合法制备了以石蜡(PA)为芯材、三聚氰胺-甲醛-树脂为壁材、碳纳米管(CNT)及纳米铜(CNP)为导热粒子的改性相变微胶囊。结果表明:随着CNT和CNP添加量的增加,CNT改性相变微胶囊(MPCM/CNTs)的导热系数从0.25W/(m·K)增大到0.38W/(m·K),最大增加率为52%;CNP改性相变微胶囊(MPCM/CNPs)导热系数从0.25W/(m·K)增大到0.47W/(m·K),最大增加率为88%。

棕榈酸定形复合相变材料研究进展

棕榈酸因存在热导率低和物态相变时易泄漏的缺点,限制了其在诸多领域的发展和应用。棕榈酸定形复合相变材料以支撑材料为基体,将棕榈酸分散在基体材料中,不仅有效解决棕榈酸的泄漏问题,而且基体材料的加入还能提高复合相变材料的热导率。综述了基于不同基体材料的棕榈酸定形复合相变材料的研究进展,指出了棕榈酸定形复合相变材料的不足之处,并展望了其未来研究方向。

桑葚花青素的稳定性及降解动力学研究

桑葚花青素不稳定,外界因素的变化容易造成其降解。该试验以花青素保留率和颜色变化为评价指标,考察了光照、pH值、温度、添加剂、金属离子等因素对桑葚花青素稳定性的影响并探究其降解动力学。结果显示:室外光照加速了花青素的降解,k值由避光条件的1.80×10^(-2)升高至14.12×10^(-2),t_(1/2)由避光条件的38.5 h降至5.2 h。酸性环境(pH值1.00,3.00)下花青素的稳定性高,中性(pH值7.00)、碱性(pH值9.00)时花青素易发生降解,96 h后花青素的保留率分别降至83.25%、72.44%,颜色由酸性时的红色分别变为灰绿色、墨绿色。花青素在80,100℃分别放置10 h后ΔE^(*)分别变为3.4097,6.1928,红色褪去,花青素的保留率仅为65.39%、38.83%。酸度剂(柠檬酸)对花青素有明显的稳定和增色作用,防腐剂(山梨酸钾、苯甲酸钠)、抗氧化剂(抗坏血酸)加速了花青素的降解。Al^(3+)、Fe^(3+)、Fe^(2+)等金属离子的加入在一定程度上破坏了花青素的结构,颜色分别变为蓝紫色、黄褐色、蓝黑色。桑葚花青素的贮藏稳定性较差,适合低温、避光和酸性环境,并避免接触防腐剂、抗氧化剂等添加剂和铁、铝制品。该试验结果为花青素的贮藏、加工和应用提供了基础数据和理论依据。

定形相变材料储热性能和强化传热研究进展

潜热蓄热技术被视为缓解能源供需矛盾的有效措施,其利用相变材料在相变过程中吸热/放热来实现能量的存储和释放,在建筑节能、温室控温、调温服装等领域具有极大的应用潜力。归纳了定形相变材料的种类和特点,对多孔基相变材料、微胶囊相变材料和聚合物基相变材料等制备技术及储热性能的研究进展进行了综述,分析了定形相变材料制备过程中存在的问题,介绍了定形相变材料的强化传热方法,最后讨论了今后研究工作的重点并展望了定形相变材料的发展前景。

PEG4000/聚苯胺形状稳定复合相变材料的制备及其储热性能

以聚苯胺气凝胶(PANI)为支撑骨架,聚乙二醇4000(PEG4000)为相变材料,银纳米线(AgNWs)为导热增强填料,采用低温氧化聚合法和真空浸渍法制备得到具有良好形状和循环稳定性的定形相变复合材料PEG4000@Ag/PANI.聚苯胺气凝胶的高孔隙率及PEG4000与基体材料间的氢键作用和毛细作用,使得相变复合材料的最高负载率能够达到94.17%(熔融焓为165.17 J·g^(–1),凝固焓为152.77 J·g^(–1));加入AgNWs与PANI气凝胶共同搭建导热通路,提高了相变复合材料的导热性能(热导率最高为0.45 W·m^(–1)·K^(–1),比纯PEG4000提高80%);借助Ag NWs和聚苯胺优异的光吸收能力,相变复合材料的光–热转换效率达到90.61%.高储能密度、高光热转换能力和高热导率定形相变复合材料的成功制备为新型相变复合材料的合成提供了新思路,为太阳能光–热转换和储能应用提供了新材料,实现对太阳能的高效利用.

LA-MA/陶粒相变储能材料热物性试验与分析

目的为拓宽相变材料在建筑节能领域中的应用,针对单一相变材料难以满足建筑热工性能要求的问题。方法以十二醇(LA)和十四酸(MA)为复合相变材料、页岩陶粒为载体,制备一种新型相变储能骨料。采用差式扫描量热仪(DSC)、傅里叶红外光谱仪(FT-IR)、热重分析仪(TG)等对相变储能骨料的热物性和不同封装方式下的相变循环稳定性进行分析。结果经复合后相变材料、相变储能骨料的相变温度和相变潜热分别为22.08℃、22.92℃和182.1J/g、22.33J/g。LA-MA复合相变材料和页岩陶粒之间仅存在物理嵌合关系,相变储能骨料在70℃以下未发生物质分解。苯丙乳液封装相变储能骨料在5℃~45℃范围内经历100次相变循环后,质量损失率为0.80%。结论LA-MA/陶粒相变储能骨料的热物性满足建筑节能要求,化学结构稳定,热稳定性好,具有优异的循环耐久性,可应用到建筑围护结构中,研究结论对相变储能材料在建筑围护结构中的应用具有参考价值。

换极对铝电解槽冲击的分析研究

本文针对换极对铝电解槽日常生产的冲击问题,从热平衡与磁流体稳定性两方面进行计算和分析,指出目前铝电解企业换极普遍存在的问题,并提出一些新的思路和想法。

气相二氧化硅/三元无机水合盐定型相变材料的制备及性能表征

以气相二氧化硅作为多孔吸附材料,对十二水磷酸氢二钠/五水偏硅酸钠/十水碳酸钠低共熔相变材料进行封装,通过控制气相二氧化硅含量,制备出不同吸附量的气相二氧化硅/三元无机水合盐定型相变材料。通过差示扫描量热仪、扫描电子显微镜、傅里叶变换红外光谱仪、X射线衍射仪和热重分析仪等多种测试手段,对定型相变材料的性能和结构进行表征。研究结果表明:气相二氧化硅的最佳含量为25%(质量分数),该条件下定型相变材料相变焓为95.96J/g;三元无机水合盐相变材料与气相二氧化硅只是单纯的物理混合,并未发生化学反应产生新物质,制备的定型相变热稳定性较好。

基于动态稳定性验证和CA-Markov预测的耕地时空演变特征--以赣榆区为例

为阐明耕地变化动态稳定性验证的重要性,预测“十四五”目标年(2025年)与远景目标年(2035年)的耕地变化,本研究运用耕地面积变异系数、地理集中指数、不平衡指数及趋势分析法,从耕地数量、空间分布与空间发展趋势三个方面,对江苏省连云港市赣榆区耕地变化的动态稳定性进行验证,并运用CA-Markov模型对未来不同政策情境下的耕地变化情况进行模拟。结果表明,2009-2016年赣榆区耕地总量持续下降,未存在较大反复与波动,耕地空间分布较为均衡,耕地占用与补充的空间发展趋势较为连续,总体上具有较高的动态稳定性,符合运用CA-Markov模型的前提条件。预测在各种政策情境下,2025年之前赣榆区将经历快速的耕地非农化过程,至2035年耕地减少的速率有所放缓,具有区位优势的赣榆北部地区将是未来耕地非农化的重点区域,耕地将逐渐向南部内陆地区转移。研究表明,对耕地变化的动态稳定性进行验证可以有效保证CA-Markov模型的模拟精度,赣榆区未来的耕地保护形势不容乐观,应合理协调经济发展与耕地保护之间的关系,保障社会、生态与粮食安全。

黑龙江干流黑河市城区段河床演变研究

黑龙江黑河市城区河段河道受自然及人为因素影响,河床演变复杂。采用Mann-Kendall趋势检验法和双累积曲线法分析了水沙变化趋势。基于实测水文和泥沙资料,对河床稳定性及冲淤变化进行了定量研究。研究结果表明,该河段属于少沙河流,结雅河口以上年径流和输沙量随时间呈减小趋势,结雅河口以下年径流没有明显的趋势性变化,年输沙量呈减小趋势。自然状态下,河段岸线和深泓线位置基本稳定,河床冲淤变化不大,以约10年为一个周期,基本可以达到冲淤平衡。在人类活动及支流汇入影响下,黑河水位站至长发岛段纵向不稳定,预测会引起该段未防护岛屿洲滩的岸线变迁。

国际贸易隐含碳转移溢出、转型风险与宏观金融稳定

在国际贸易、环境经济与气候金融相互影响的背景下,本文通过构建可以观察碳转移溢出效应的全球碳转移联通网络,实证分析了碳转移溢出对宏观金融稳定的影响及传导机制。结果表明:各经济体之间碳转移溢出明显降低了经济发展水平较低、气候损失较大以及气候表现绩效较差经济体的金融稳定水平,特别是增加了经济体的外债清偿风险、经常账户余额风险和国际储备流动性风险,资产价格重估视角下的转型风险是其中介机制。此外,本文还发现气候适应性措施能够有效减缓碳转移溢出对宏观金融稳定的影响,相比之下,现有的绿色宏观审慎监管框架需要进一步完善。本文探讨了气候金融框架下气候变化影响宏观金融稳定的一个可能传导链条,为从双循环视角推进我国经济绿色发展提供了新的证据。

某水库水位变化对库区围堰坝体边坡稳定性的影响

为查明水库围堰边坡设计的合理性及水位变化对边坡稳定性的影响,基于FLAC3D数值模拟软件,针对百色市某水库建立三维模型,模拟了围堰边坡在水位下降、水位上升和基坑排水3种情景下的变形情况,分析了水位变化对边坡稳定性的影响。结果表明,围堰边坡上游一、二级台阶及下游二级台阶区域易发生较大变形;库水位下降引起各监测点水平位移为40~230 mm、竖向位移为260~390 mm,库水位上升引起各监测点水平位移为60~360 mm、竖向位移约为150 mm,基坑排水引起各监测点水平位移为580~600 mm、竖向位移为21~57 mm,对围堰边坡变形的影响大小依次为基坑排水>库水位下降>库水位上升;边坡安全系数与水位变化呈正相关关系,安全系数增量随水位上升先增大后减小。研究结果为边坡设计和防护提供了理论依据。

面向短时/断续工作制的电机系统固–液相变热管理技术及应用发展

固–液相变现象表现出的潜热特性可有效平抑瞬时温升,将其应用于航天航空、奔越式机器人、新能源汽车、数控机床等电机热管理系统,可有效提高短时工作制或断续周期性工作制(S2—S8)下运行的伺服电驱动系统的瞬态性能。为了总结归纳固–液相变材料的电机系统热管理技术及其应用现状,该文针对固–液相变材料特性、系统数值计算与仿真模拟、样机实验测试方法、相变热管理系统结构等4个方面开展调研,并提出亟待解决的关键技术问题。研究发现:目前阶段石蜡和低温熔盐是适合电机系统的最佳相变介质,但仍存在导热系数较低的问题,需通过改性强化解决;通过机壳灌注相变材料,可有效实现温升平抑,但尚缺乏有针对性的热路拓扑设计;采用焓–多孔方法是模拟相变过程的理想手段,但糊状区参数的取值缺乏理论指导;最后,固–液相变过程的测试中侵入式传感器易对电磁、热、流场的自然演变过程产生干扰。