Chemical Ecology of Cave-Dwelling Millipedes: Defensive Secretions of the Typhloiulini (Diplopoda,Julida, Julidae)

Cave animals live under highly constant ecological conditions and in permanent darkness, and many evolutionary adaptations of cave-dwellers have been triggered by their specific environment. A similar “cave effect” leading to pronounced chemical interactions under such conditions may be assumed, but the chemoecology of troglobionts is mostly unknown. We investigated the defensive chemistry of a largely cave-dwelling julid group, the controversial tribe “Typhloiulini”, and we included some cave-dwelling and some endogean representatives. While chemical defense in juliform diplopods is known to be highly uniform, and mainly based on methyl- and methoxy-substituted benzoquinones, the defensive secretions of typhloiulines contained ethyl-benzoquinones and related compounds. Interestingly, ethyl-benzoquinones were found in some, but not all cave-dwelling typhloiulines, and some non-cave dwellers also contained these compounds. On the other hand, ethyl-benzoquinones were not detected in troglobiont nor in endogean typhloiuline outgroups. In order to explain the taxonomic pattern of ethyl-benzoquinone occurrence, and to unravel whether a cave-effect triggered ethyl-benzoquinone evolution, we classed the “Typhloiulini” investigated here within a phylogenetic framework of julid taxa, and traced the evolutionary history of ethyl-benzoquinones in typhloiulines in relation to cave-dwelling. The results indicated a cave-independent evolution of ethyl-substituted benzoquinones, indicating the absence of a “cave effect” on the secretions of troglobiont Typhloiulini. Ethyl-benzoquinones probably evolved early in an epi- or endogean ancestor of a clade including several, but not all Typhloiulus (basically comprising a taxonomic entity known as “Typhloiulus sensu stricto”) and Serboiulus. Ethyl-benzoquinones are proposed as novel and valuable chemical characters for julid systematics.     

一种四足式爬壁机器人控制系统的研究

四足式爬壁机器人控制系统采用分级控制的分布式结构,上位机采用ARM结构的高级单片机,下位机采用微型直流电机伺服控制器,通讯方式采用RS232总线．文章介绍了该控制系统的软硬件体系结构,以及通讯管理模式．分析表明该控制系统方案及设计是可行的．     

通信铁塔的设计与维护探讨

随着通信行业的快速发展通信业务量越来越大,需要建设的通信铁塔数量也跟着增多.本文结合通信铁塔概述探讨了通信铁塔的设计与维护.     

自由曲面微铣刀加工路径建模与仿真

为提高微小自由曲面数控加工精度与效率,对选择高效的自由曲面微铣刀加工路径进行了研究和讨论。在UG软件中,不同的加工模式对于自由曲面可得到不同的加工路径。首先,建立自由曲面模型并选定加工参数;然后,选用三种不同的加工方法,分别跟随周边、单向和往复,对三种加工路径进行铣削加工编程与仿真,分析了不同加工路径过切量与欠切量的结果,并对每种路径的加工时间进行了比较;最后,根据仿真及分析结果确定了具有较好加工精度和高效的加工路径。仿真结果表明,单向方式的加工路径可获得最小过切量,而往复加工路径可获得最小的欠切量。在加工时间方面,三种加工路径跟随周边、单向和往复的铣削时间分别为53s、115s和65s。通过对三种路径的分析与比较,选择高效的加工路径,帮助提高生产效率和加工精度。     

吸油烟机风量测试研究

吸油烟机现已成为现代家庭必不可少的家用电器之一.通过测试对比吸油烟机风量方面国标和IEC标准测试方法之间的差异,发现普通住宅由于公共烟道的限制,风量过大不仅不能发挥更好的排烟效果,而且还会对烹饪时产生的油烟流动方向产生干扰.吸油烟机风量的测试方法国标和IEC标准存在一些差异,在吸油烟机产品出口到欧洲时,就需要注意产品性能标准的差异,也为之后标准测试方法的制定提供参考.     

家用电器舒适性自然风技术研究

随着人们对于物质生活要求的不断提高,人们对于室内环境的舒适性要求也越来越高,空调、电风扇、新风机等家电产品的能耗也随着增加.而室内空调环境中,环境温度变化小,缺少环境刺激,会导致人体的温度适应能力下降,甚至是抵抗力减弱.相比空调、电风扇、新风机等家电产品单调的机械风,自然风以清新、多变、柔和的吹风感而受到人们的偏爱.综合能源问题和舒适度两个方面来看,研究自然风的特性,采用模拟自然风送风方式能更好的改善室内居住环境,提高人体舒适度.     

家用电器舒适性自然风技术研究

随着人们对于物质生活要求的不断提高,人们对于室内环境的舒适性要求也越来越高,空调、电风扇、新风机等家电产品的能耗也随着增加.而室内空调环境中,环境温度变化小,缺少环境刺激,会导致人体的温度适应能力下降,甚至是抵抗力减弱.相比空调、电风扇、新风机等家电产品单调的机械风,自然风以清新、多变、柔和的吹风感而受到人们的偏爱.综合能源问题和舒适度两个方面来看,研究自然风的特性,采用模拟自然风送风方式能更好的改善室内居住环境,提高人体舒适度.     

基于电场有限元分析的非接触法相对介电常数测量结果的修正方法

为了提高基于非接触法的相对介电常数测量的准确性,利用电场有限元分析建立对应的模型并获得了电极及其附近的电场和电位分布.分析了电极系统存在的边缘效应,给出了其对相对介电常数测量结果的影响.分析了潜在因素对非接触法测量误差的影响,确定了修正时需要考虑的因素为电极间隙距离、试样厚度与电极间隙距离之比和试样的相对介电常数.根据电极间隙距离、距离比、相对介电常数测量值到相对介电常数真实值的关系,采用三维插值法和匹配法修正测得的相对介电常数.采用仿真对修正方法进行了验证并针对实测高温硫化硅橡胶相对介电常数使用了该方法,结果验证了该方法的有效性.结果 表明:随着电极间隙距离和试样相对介电常数的增加误差幅值增大,随距离比的增加误差存在减小的趋势.对电极间隙距离、距离比和相对介电常数分别在0.2～5 mm、0.5～1和1～20内建模获得2 380组相对介电常数的真实值和计算值,发现相对误差在-0.37％～-41.72％内变化.     

Fixed‐time attitude tracking control for spacecraft based on adding power integrator technique

In this article, the fixed‐time attitude tracking problem for rigid spacecraft is investigated based on the adding‐a‐power‐integrator control technique. First, a fixed‐time attitude tracking controller is designed to guarantee fixed‐time convergence of tracking errors. Then, by considering the presence of random disturbance and actuator faults, an adaptive fault‐tolerant attitude tracking controller is designed to guarantee tracking errors converge to a residual set of zero in a fixed time. The complete bounds on settling time are derived independently of initial conditions. The simulation results illustrate the highly precise and robust attitude control performance obtained by using the proposed controllers.     

In situ growth of Co3O4 nanoneedles on titanium mesh for electrocatalytic oxygen evolution

Designing high-efficient and low cost of electrodes with seamless integration of substrate and electrocatalyst particles is of significant concern for electrocatalytic water splitting. In this study, we actualized in situ growth of Co₃O₄ nanoneedles on titanium (Ti) mesh (denoted as Co₃O₄@Ti) by a simple combination of hydrothermal approach and subsequently calcination treatment under relatively low temperatures. The as-prepared Co₃O₄@Ti samples were evaluated as anodes for electrocatalytic oxygen evolution reaction (OER) in alkaline electrolyte. It demonstrates that the optimized Co₃O₄@Ti electrode displayed good OER activity with a small overpotential of 416 mV at a current density of 20 mA cm^?2, which is on a par with commercial RuO₂ catalyst (overpotential of 403 mV at 20 mA cm^?2). The satisfactory OER performance of Co₃O₄@Ti electrode is largely attributed to the seamless integration of conductive Ti mesh substrate and the direct growth of Co₃O₄ nanoneedles on Ti mesh with sufficient active sites. This study suggests the potential application of Co₃O₄@Ti electrode as preeminent OER catalyst.