Finite-time and fixed-time sliding mode control for second-order nonlinear multiagent systems with external disturbances

In this paper, the leader-following consensus of second-order nonlinear multiagent systems (SONMASs) with external disturbances is studied. Firstly, based on terminal sliding model control method, a distributed control protocol is proposed over undirected networks, which can not only suppress the external disturbances, but also make the SONMASs achieve consensus in finite time. Secondly, to make the settling time independent of the initial values of systems, we improve the protocol and ensure that the SONMASs can reach the sliding surface and achieve consensus in fixed time if the control parameters satisfy some conditions. Moreover, for general directed networks, we design a new fixed-time control protocol and prove that both the sliding mode surface and consensus for SONMASs can be reached in fixed time. Finally, several numerical simulations are given to show the effectiveness of the proposed protocols

Oxidation Degradation of Rhodamine B in Aqueous by UV

The UV photolysis of persulfate (S2O8 2−) is a novel advanced oxidation technologies (AOTs), which leads to the formation of strong oxidizing radicals, sulfate radicals (SO4 •−). The effect of oxidant S2O8 2− concentration, initial dye concentration, initial pH of solution, and various inorganic anions (Cl−, H2PO4 −, and HCO3 −) were investigated using Rhodamine B (RhB), a kind of xanthene dye, as a model pollutant. With the increase of oxidant S2O8 2−, more SO4 •− produced to attack RhB molecules and result in the increase of RhB degradation. While the improvement was not sustained above a critical value, beyond which degradation rate does not increase. Initial pH of solution had great effect on the RhB degradation rate during UV/S2O8 2− system. SO4 •− is rather stable in acidic solutions, while increasing system pH results in the transformation of SO4 •− to •OH. The effects of three inorganic anions (Cl−, H2PO4 −, and HCO3 −) all had some negative effect on the degradation of RhB. Based on the RhB solution changes of the UV-vis absorption intensity during the UV/S2O8 2− treatment, decolorization of RhB accompanied the destruction of aromatic ring structures of RhB molecules

Coherent Compensation based ISAC Signal Processing for Long-range Sensing

Integrated sensing and communication (ISAC) will greatly enhance the efficiency of physical resource utilization. The design of ISAC signal based on the orthogonal frequency division multiplex (OFDM) signal is the mainstream. However, when detecting the long-range target, the delay of echo signal exceeds CP duration, which will result in inter-symbol interference (ISI) and inter-carrier interference (ICI), limiting the sensing range. Facing the above problem, we propose to increase useful signal power through coherent compensation and improve the signal to interference plus noise power ratio (SINR) of each OFDM block. Compared with the traditional 2D-FFT algorithm, the improvement of SINR of range-doppler map (RDM) is verified by simulation, which will expand the sensing range

A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes

Due to the broad applications of porous alumina nanostructures, research on fabrication of anodized aluminum oxide (AAO) with nanoporous structure has triggered enormous attention. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, it is known that its growth rate can be easily affected by the fluctuation of process conditions such as acid concentration and temperature during electrochemical anodization process. To fabricate AAO with various geometric parameters, particularly, to realize precise control over pore depth for scientific research and commercial applications, a controllable fabrication process is essential. In this work, we revealed a linear correlation between the integrated electric charge flow throughout the circuit in the stable anodization process and the growth thickness of AAO membranes. With this understanding, we developed a facile approach to precisely control the growth process of the membranes. It was found that this approach is applicable in a large voltage range, and it may be extended to anodization of other metal materials such as Ti as well.Hong Kong Research Grant Council [612113]; Hong Kong Innovation Technology Commission [ITS/362/14FP]; Fundamental Research Project of Shenzhen Science & Technology Foundation [JCYJ20130402164725025]; National Natural Science Foundation of China [61574005]; Priority Academic Program Development of Jiangsu Higher Education Institutions [PAPD]SCI(E)[email protected]; [email protected]

Accumulation of perfluoroalkyl compounds in Tibetan mountain snow:temporal patterns from 1980 to 2010

The use of snow and ice cores as recorders of environmental contamination is particularly relevant for per- and polyfluoroalky substances (PFASs) given their production history, differing source regions and varied mechanisms driving their global distribution. In a unique study perfluoroalkyl acids (PFAAs) were analyzed in dated snow-cores obtained from high mountain glaciers on the Tibetan Plateau (TP). One snow core was obtained from the Mt Muztagata glacier (accumulation period of 1980–1999), located in western Tibet and a second core from Mt. Zuoqiupo (accumulation period: 1996–2007) located in southeastern Tibet, with fresh surface snow collected near Lake Namco in 2010 (southern Tibet). The higher concentrations of ∑PFAAs were observed in the older Mt Muztagata core and dominated by perfluorooctanesulfonic acid (PFOS) (61.4–346 pg/L) and perfluorooctanoic acid (PFOA) (40.8–243 pg/L), whereas in the Mt Zuoqiupu core the concentrations were lower (e.g., PFOA: 37.8–183 pg/L) with PFOS below detection limits. These differences in PFAA concentrations and composition profile likely reflect the upwind sources affecting the respective sites (e.g., European/central Asian sources for Mt Muztagata and India sources for Mt Zuoqiupu). Perfluorobutanoic acid (PFBA) dominated the recent surface snowpack of Lake Namco which is mainly associated with India sources where the shorter chain volatile PFASs precursors predominate. The use of snow cores in different parts of Tibet provides useful recorders to examine the influence of different PFASs source regions and reflect changing PFAS production/use in the Northern Hemisphere

On the Management and Legislation of Mangrove Natural Reserves in China

*梅宏,男,厦门大学法学博士后流动站研究人员,中国海洋大学法政学院副教授,研究方向:国际法学,环境法学。电子邮箱:[email protected]。**薛志勇,福建省龙海市林业局高级工程师,法律硕士。［文摘］红树林系指红树林湿地中的林地,其仅为红树林湿地生态系统的一部分。区分红树林和红树林湿地,应考虑它们不同的特点对其加以保护。然而,在中国,红树林被认为属于“森林”范畴,有关红树林的法律法规多由林业部门制定,且远远不能满足实践的要求;在保护和管理红树林湿地方面,人们多效仿和沿用陆地森林的标准。忽视湿地生态系统的完整性,是中国红树林保护存在的又一主要问题。国内大部分红树林保护区的保护方式还停留在“看林子”水平,而非视其为一个整体的生态系统来保护。更糟的是,缺少一个特别机构协调林业部门、海洋部门以及其他监管部门在红树林保护工作中的权利义务关系,由此,难以避免各部门之间的法律冲突。针对中国红树林保护区管理与立法的问题,提出如下建议:其一,非政府监督机制应被引入红树林保护与管理;其二,完善公众参与机制,积极保护生态利益;其三,为了更有效地保护红树林,各红树林保护区应制定自己的条例。［Abstract］Mangroves refer to the forested land in the mangrove wetland,and are only part of the ecosystem of the mangrove wetland.As mangroves and mangrove wetlands are two distinct entities,the practices of protecting them should accordingly take into consideration their unique features.However,in China,mangroves are classified as simply“forest”,thus the Mangrove Protection Laws and Regulations,which are far from sufficient,are drafted and implemented by the government’s forestry department/division.As a result,mangroves are managed and protected in the same way as forest land.Ignoring the integrity of the wetland ecosystem is another obstacle to protecting mangroves in China.The typical approach to protecting mangroves in China is “nursing only the woods”,rather than the ecosystem as a whole.To make matters worse,there is no special agency to coordinate the authorities under different departments,such as the forestry department,marine department,and the other departments that oversee the mangroves in some way.As a result,it is very difficult to avoid juridical conflicts among various departments.This paper provides some suggestions on the management and legislation of mangrove natural reserves in China.Firstly,non-governmental monitoring mechanisms should be incorporated into the management and protection of mangrove wetlands.Secondly,we need to improve public participation and to protect the ecological interest actively.Thirdly,each mangrove natural reserve should have its own regulations in order to protect mangroves more effectively.中国博士后科学基金面上资助项目“滨海湿地保护法律问题研究”(20100470874),梅宏主持