基于粒子群优化多核支持向量数据描述的广播式自动相关监视异常数据检测模型

广播式自动相关监视(ADS-B)作为新一代空中交通管理(ATM)通信协议,是未来空管监视系统的关键技术。目前,由于ADS-B采用明文格式广播发送数据,其安全性问题受到挑战。针对ADS-B易受到的欺骗干扰,该文将ADS-B位置数据和同步的二次雷达(SSR)数据作差,将两者的差值作为样本数据。利用多核支持向量数据描述(MKSVDD)训练样本,得到了超球体分类器,此超球体分类器能检测出ADS-B测试样本中的异常数据。并且,通过粒子群算法(PSO)优化了GaussLapl和GaussTanh两种MKSVDD的惩罚因子、多核核函数系数以及核参数,提高了异常数据检测性能。实验结果表明,对于随机位置偏移、固定位置偏移、拒绝服务(DOS)攻击和重放攻击,粒子群优化多核支持向量数据描述(PSO-MKSVDD)模型能检测出这4种攻击类型的异常数据。且相较于其他机器学习和深度学习方法,该模型的适应性更好,异常检测的召回率和检测率更优。证明该模型可用于ADS-B异常数据的检测。     

Colorimetric Detection of Small Molecules by a Frustrated Lewis Pair Containing a Phosphorus-Functionalized Cycloheptatrienyl?Cyclopentadienyl Titanium Sandwich Complex

The phosphorus-functionalized cycloheptatrienyl cyclopentadienyl (Cht Cp) titanium sandwich complex [(η⁷-C₇H₇)Ti(η⁵-C₅H₄PtBu₂)] ( 7 ) forms a frustrated Lewis pair (FLP) in combination with the borane B(C₆F₅)₃, and this FLP undergoes heterolytic cleavage of dihydrogen and fixation of carbon dioxide and nitrous oxide with a noticeable colorimetric response, which is visible to the naked eye. In their UV/Vis spectra, the H₂, CO₂ and N₂O fixation products exhibit a bathochromic shift of the absorption band that can be assigned to a HOMO LUMO excitation of the Cht Cp titanium (troticene) moiety.     

DDCA-WSN: A Distributed Data Compression and Aggregation Approach for Low Resources Wireless Sensors Networks

Wireless Sensor Networks (WSN) have been as useful and beneficial as resource-constrained distributed event-based system for several scenarios. Yet, in WSN, optimisation of limited resources (energy, computing memory, bandwidth and storage) during data collection and communication process is a major challenge. Data redundancy involves a large consumption of sensor resources during processing and transferring information to an analysis centre. As a matter of fact, most of energy consumption (as much as 80%) for standard WSN applications lies in the radio module where receiving and sending packets is necessary to communicate between stations.  Thus, this paper proposes an approach to achieve optimal sensor resources by data compression and aggregation regarding integrity of raw data. Then, the main objective is to reduce this redundancy by discarding a certain number of packets of information and keeping only the most meaningful and informative ones for the reconstruction. Data aggregation discarded a certain sensing data packet, which lead to low data-rate communication and low likelihood of packet collisions on the wireless medium. Data compression reduces a redundancy in keeping aggregated data, in order to diminish resources consumption of wireless sensor nodes, which leads to storage saving and sending only a small data stream in the bandwidth of communication. The performances of the proposed approach DDCA-WSN are qualified using experimental simulation on OMNeT++/Castalia. The performance metrics were evaluated in terms of Compression Ratio (CR), data Aggregation Rate (AR), Peak Signal-to-Noise Ratio (PSNR), Mean Square Error (MSE) and Energy Consumption (EC).The obtained results have significantly increased the network lifetime. Moreover, the integrity (quality) of the raw data is guaranteed.

     

Core-shell structured photovoltaic devices based on PbS quantum dots and silicon nanopillar arrays

We fabricated three-dimensional silicon nanopillar array (SiNP)-based photovoltaic (PV) devices using PbS quantum dots (QDs) as the hole-transporting layers. The core-shell structured device, which is based on high aspect ratio SiNPs standing on roughed silicon substrates, displays a higher PV performance with a power conversion efficiency (PCE) of 6.53% compared with that of the planar device (2.11%). The enhanced PCE is ascribed to the increased light absorption and the improved charge carrier collections in SiNP-modified silicon surfaces. We also show that, for the core-shell structured device, the thickness of the shell layer plays a critical role in enhancing the PV performance and around five monolayers of QDs are preferred for efficient hole-transporting. Wafer-scale PV devices with a radial PbS/SiNP heterojunction can be fabricated by solution phase techniques at low temperatures, suggesting a facile route to fabricate unique three-dimensional nanostructured devices.     

ADS-B攻击数据弹性恢复方法

为了对自动广播相关监视(ADS-B)攻击数据进行弹性恢复,确保空情态势感知信息的持续可用性,该文提出针对ADS-B攻击数据的弹性恢复方法。基于前置的攻击检测机制,获取当前ADS-B量测数据序列和预测数据序列,并在此基础上构建偏差数据序列、差分数据序列和邻近密度数据序列。依托偏差数据构建恢复向量,依托差分数据挖掘攻击数据的时序特性,依托邻近密度数据挖掘攻击数据的空间特性。通过整合3种数据序列构建弹性恢复策略并确定恢复终止点,实现对攻击影响的弱化,将ADS-B攻击数据向正常数据方向进行定向恢复。通过对6种典型攻击样式的实验分析,证明该弹性恢复方法能够有效恢复ADS-B攻击数据,削弱数据攻击对监视系统的影响。     

产油脂海洋微藻的筛选、鉴定及Fe3+对其生长和油脂积累的影响

采用尼罗红染色和油脂提取相结合的方法,从105株海洋微藻中,筛选并鉴定了1株油脂产量较高的微藻琴式菱形藻(Psammodictyon panduriforme),研究了Fe3+对其生长和油脂积累的影响.结果表明,添加Fe3+有利于Psammodictyon panduriforme的生长和油脂积累,在Fe3+浓度为4×10-4mol/L时,其生物量最大(0.65 g/L),油脂含量最高(49.07％),此时的油脂产量也最高,达到了318.96 mg/L,是不加Fe3+培养的6.15倍.     

基于鲁棒主成分分析的智能电网虚假数据注入攻击

基于主成分分析（PCA）的盲攻击策略仅对具有高斯噪声的测量数据有效,在存在异常值的情况下,上述攻击策略将被传统的坏数据检测模块检测。针对异常值存在的问题,提出一种基于鲁棒主成分分析（RPCA）的盲攻击策略。首先,攻击者收集含有异常值的测量数据;然后,通过基于交替方向法（ADM）的稀疏优化技术从含有异常值的测量数据中分离出异常值和真实的测量数据;其次,对真实测量数据进行PCA,得到系统的相关信息;最后,利用获得的系统信息构造攻击向量,并根据得到的攻击向量注入虚假数据。该攻击策略在IEEE 14-bus系统上进行了测试,实验结果表明,在异常值存在的情况下,传统的基于PCA的攻击方法将被坏数据检测模块检测,而所提方法基于鲁棒PCA的攻击策略能够躲避坏数据检测模块的检测。该策略使得在异常值存在的情况下虚假数据注入攻击（FDIA）仍然能够成功实施。     

Investigation of the Physical and Mechanical Properties of Raffia Vinifera Fibers along the Stem

The study of the physical and mechanical properties of raffia vinifera fibers along the stem is examined in this work. In central Africa, these fibers are already being used by craftsmen in the field of textile and decoration. The cross-section of fibers is higher at the base of the stem and grows from the periphery toward the center on a transverse position. By the Archimedes method, the obtained bulk density was between 0.1288 g/cm³ and 0.2368 g/cm³ and in a transverse position, it increases from the center toward the periphery. The dynamic tensile tests were used to estimate the Young’s modulus that lies among 0.88 GPa and 7.9 GPa and the low values are at the base of the stem. The specific Young’s modulus was deduced and varied from 7.33 GPa/(g/cm³) and 66.00 GPa/(g/cm³). Finally, through the strain, the microfibril angle was found and it is oscillated from 29.81° to 48.65°.     

Lithography-free fabrication of silicon nanowire and nanohole arrays by metal-assisted chemical etching

We demonstrated a novel, simple, and low-cost method to fabricate silicon nanowire (SiNW) arrays and silicon nanohole (SiNH) arrays based on thin silver (Ag) film dewetting process combined with metal-assisted chemical etching. Ag mesh with holes and semispherical Ag nanoparticles can be prepared by simple thermal annealing of Ag thin film on a silicon substrate. Both the diameter and the distribution of mesh holes as well as the nanoparticles can be manipulated by the film thickness and the annealing temperature. The silicon underneath Ag coverage was etched off with the catalysis of metal in an aqueous solution containing HF and an oxidant, which form silicon nanostructures (either SiNW or SiNH arrays). The morphologies of the corresponding etched SiNW and SiNH arrays matched well with that of Ag holes and nanoparticles. This novel method allows lithography-free fabrication of the SiNW and SiNH arrays with control of the size and distribution.     

Fusarium pallidoroseum in maize samples of three agro-ecological zones of Cameroon

Investigations were conducted to determine the presence of mycotoxigenic fungi in maize samples from Cameroon. The deep freezing blotter method, and the medium DG-18, with and without 1% sodium hypochlorite surface sterilization pre-treatment, were used. The plated grains were incubated for 7 days under a cycle of 12 h (NUV) daylight and 12 h darkness. Fusarium pallidoroseum was found infecting 1-2% of the tested grains. Eleven samples out of 65 tested were found infected, 2 samples from the locality of Melong in the humid forest agro-ecological zone with monomodal rainfall, 1 from Foumbot and 2 from Bamenda in the highlands agro-ecological zone, and 6 from Yaounde, in the humid forest with bimodal rainfall agro-ecological zone. An infection rate of 2% of the grains was found on blotter paper while only 1% was recorded on the reduced water activity medium DG-18, with or without surface sterilization. F. pallidoroseum is reported here for the first time from maize samples of Cameroon. This underlines the need for detailed research on toxigenic fungi and the improvement of common storage practices to avoid mycotoxin contamination and the resulting human and animal health problems.