Robust Control of a Bevel-Tip Needle for Medical Interventional Procedures

In minimally invasive surgery, one of the main objectives is to ensure safety and target reaching accuracy during needle steering inside the target organ. In this research work, the needle steering approach is determined using a robust control algorithm namely the integral sliding mode control(ISMC) strategy to eliminate the chattering problem associated with the general clinical scenario. In general, the discontinuity component of feedback control input is not appropriate for the needle steering methodology due to the practical limitations of the driving actuators. Thus in ISMC, we have incorporated the replacement of the discontinuous component using a super twisting control(STC)input due to its unique features of chattering elimination and disturbance observation characteristics. In our study, the kinematic model of an asymmetric flexible bevel-tip needle in a soft-tissue phantom is used to evaluate stability analysis. A comparative study based on the analysis of chattering elimination is executed to determine the performance of the proposed control strategy in real-time needle steering with conventional sliding mode control using vision feedback through simulation and experimental results. This validates the efficacy of the proposed control strategy for clinical needle steering.     

Small hydropower dam alters the taxonomic composition of benthic macroinvertebrate assemblages in a neotropical river

Hydropower dams substantially modify lotic ecosystems. Most studies regarding their ecological impacts are based on large dams and provide little information about the far more abundant effects of small hydropower dams. Our aim was to characterize the ecological effects of a small hydropower dam and run‐of‐the‐river reservoir on the structure of benthic macroinvertebrate assemblages in the Pandeiros River located in the neotropical savanna of Brazil. We tested the hypothesis that benthic macroinvertebrate assemblages in sites directly affected by the dam and reservoir would show a different taxonomic structure compared with those in free‐flowing sites. We expected to find sensitive native species associated with the free‐flowing sites, whereas resistant and non‐native invasive taxa were expected in impounded sites. We also explored associations between the presence of native and non‐native invasive taxa to each habitat type. We found that the structure of benthic macroinvertebrate assemblages was significantly different between free‐flowing and impounded sites. Also, we found that the dam and reservoir facilitated colonization of non‐native invasive species (Corbicula fluminea and Melanoides tuberculata) because only in those sites they were found in high abundance, in contrast to the free‐flowing sites. Although the environmental conditions imposed by the impoundment altered the structure of benthic macroinvertebrate assemblages, the effects were limited to sites closest to the dam. Our results highlight the necessity of understanding physical habitat changes caused by the presence and management of run‐of‐the‐river dams and reservoirs.     

新型差分进化模型的多等级子群杂草优化算法

针对标准杂草优化算法易出现的早熟、后期收敛速度慢、易陷于局部最优等问题,提出基于新型差分进化模型的多等级子群杂草优化算法（DEMIWO）。首先,引入一种改进型的混合混沌系统对种群进行初始化,提高初始种群的多样性;其次,提出一种按等级分类的组群策略,将种群按适应度分为优、良、中、差四个等级;最后,在繁殖进化阶段,提出新型差分进化模型,对模型中的交叉变异概率进行指数式的非线性动态调整,提高算法的全局寻优能力以及收敛精度。在8个标准测试函数上进行的仿真实验表明,与标准IWO算法及其他常用算法相比,所提算法具有更快的收敛速度和更高的寻优精度,同时能有效避免陷入局部最优。     

变邻域杂草算法在多目标柔性作业车间调度中的应用*

针对最小化最大完工时间、总机床负荷最小及最大负载最小的多目标柔性作业车间调度问题,提出了变邻域杂草算法。首先,基于随机键编码方式,构造单链杂草,实现了杂草空间到调度空间的映射。其次,迭代后期执行变邻域搜索,对精英杂草局部深入挖掘,并通过反解码过程将调度空间的优良解反馈回杂草空间。对比实验表明,变邻域杂草算法在求解多目标基准问题时,非劣解集中解的数量和质量有一定优势。变邻域杂草算法是求解多目标柔性作业车间调度问题的有效方法。     

From the Source to the Outlet: understanding the Distribution of Invasive Knotweeds along a North American River

Understanding the drivers of exotic plant invasions along waterways is crucial for helping environmental managers devise effective control strategies. We combined a field survey, molecular data and a logistic regression model to further our understanding of the spatial distribution of Japanese (Fallopia japonica) and Bohemian (Fallopia × bohemica) knotweeds along the entire course (185 km) of a river located in Québec (Canada). Both knotweeds were abundant along the river, but each had a distinct spatial distribution pattern. Only one genotype for each knotweed species or hybrid was found, suggesting that the individuals established along the Chaudière River resulted from the propagation of rhizome or stem fragments. The distance from the nearest town or village was the only explanatory variable significantly correlated to the spatial distribution of knotweeds. However, spatial autoregressive coefficients were significant, indicating that knotweeds were more likely to occur close to other knotweeds. In summary, the invasion was probably initiated by the introduction, in riverside towns and villages, of a few individuals of the same genotype. The clones then spread vegetatively, probably during spring floods. The rhizome and stem fragments spread over short distances, dispersing downstream from urban centres. The introduction of just two knotweed genotypes along the Chaudière River was sufficient to initiate a massive riverside colonization, as few riparian vegetation types were apparently able to resist knotweed invasion. Copyright © 2015 John Wiley & Sons, Ltd.     

A Community‐Level,Mesoscale Analysis of Fish Assemblage Structure in Shoreline Habitats of a Large River Using Multivariate Regression Trees

The mesoscale (10⁰–10² m) of river habitats has been identified as the scale that simultaneously offers insights into ecological structure and falls within the practical bounds of river management. Mesoscale habitat (mesohabitat) classifications for relatively large rivers, however, are underdeveloped compared with those produced for smaller streams. Approaches to habitat modelling have traditionally focused on individual species or proceeded on a species‐by‐species basis. This is particularly problematic in larger rivers where the effects of biological interactions are more complex and intense. Community‐level approaches can rapidly model many species simultaneously, thereby integrating the effects of biological interactions while providing information on the relative importance of environmental variables in structuring the community. One such community‐level approach, multivariate regression trees, was applied in order to determine the relative influences of abiotic factors on fish assemblages within shoreline mesohabitats of San Pedro River, Chile, and to define reference communities prior to the planned construction of a hydroelectric power plant. Flow depth, bank materials and the availability of riparian and instream cover, including woody debris, were the main variables driving differences between the assemblages. Species strongly indicative of distinctive mesohabitat types included the endemic Galaxias platei. Among other outcomes, the results provide information on the impact of non‐native salmonids on river‐dwelling Galaxias platei, suggesting a degree of habitat segregation between these taxa based on flow depth. The results support the use of the mesohabitat concept in large, relatively pristine river systems, and they represent a basis for assessing the impact of any future hydroelectric power plant construction and operation. By combing community classifications with simple sets of environmental rules, the multivariate regression trees produced can be used to predict the community structure of any mesohabitat along the reach. Copyright © 2015 John Wiley & Sons, Ltd.     

汽车信息安全攻防关键技术研究进展

汽车技术的迅猛发展,车载信息系统的智能化、电子化水平不断提高,促使了车辆信息安全问题已经成为近年来最热门的研究领域之一。为提高车载信息系统抗攻击能力、实现汽车的安全平稳运行,从信息安全的角度,综述了汽车入侵式攻击与车辆信息安全防护保障措施理论与关键技术：对现代汽车的车载信息系统概念、结构、软件标准化等进行了详细的论述;对汽车的功能性安全、信息系统安全的区别进行了详细对比;对现代汽车入侵式攻击的方法与种类,及安全防护保障策略等进行了深入剖析;对汽车信息安全领域的国内外研究进展情况作了概括性总结;最后给出了汽车信息安全领域的发展趋势及展望。     

Eucalyptus Camaldulensis Invasion in Riparian Zones Reveals Few Significant Effects on Soil Physico‐Chemical Properties

Many invasive alien plants alter soil‐nutrient regimes of invaded ecosystems, affecting management outcomes. We assessed the effects of Eucalyptus camaldulensis invasions on physical and chemical properties of riparian soils in the Western Cape Province, South Africa. Samples were collected from topsoil beneath the canopy of uninvaded and a gradient of invaded sites, namely, light, moderate and heavy over four seasons. We quantified soil moisture, temperature, litter depth and thickness, primary textural components, concentrations of soil macro (C, N, P and K) and micro (Mn, Zn, Cu and Fe) nutrients, and pH. Available N (NO₃^?‐N and NH₄⁺‐N) and P, as well as exchangeable Ca and Mg were also assessed. Soil pH levels were significantly lower in invaded than in uninvaded sites in all seasons. Soil moisture decreased consistently with invasion intensity. Concentrations of macro, micro and available nutrients did not vary significantly along the invasion gradient (p > 0.05), but exchangeable cation content was significantly higher in uninvaded than in invaded sites, especially in winter and spring. Sites invaded by E. camaldulensis had higher litter build‐up than non‐invaded sites, but this appears to have little effect on soil‐nutrient regimes. It appears that restoration following removal of invasive stands of E. camaldulensis will not require major interventions to return soil to pre‐invasion conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Status,ecological services and management of aquatic weeds of floodplain wetlands in India: An overview

Floodplain wetlands of India are biologically rich and productive ecosystems that support unique aquatic flora and fauna. Covering an area of about 0.354 million ha, the floodplain wetlands are a major source of self‐recruiting small indigenous fish (SIF). They offer vast potential for both capture and culture‐based fisheries, securing livelihood and nutrition for a large section of the population. In addition to tremendous anthropogenic pressures and climatic variability, these resources have experienced a significant reduction in their geographical and areal extent. Aquatic macrophytes infestation in Indian floodplain wetlands is posing serious challenges to their ecological and economic functioning. Degradation and shrinkage of these important resources have been observed over the past few decades, attributable to the spread of aquatic weed infestation, warranting urgent attention in regard to their conservation and restoration to address their impending challenges. The present study compiled a total of 530 species under 103 families of aquatic macrophyte, representing four Indian states of the Ganga and Brahmaputra river basin. Among these 530 species, 85 species exhibit medicinal values and 30 species are edible, whereas some other species are used for basketry, cordage, fodder and as dye. Accordingly, the present study reviews the present status of the floodplain wetlands, their common aquatic weeds and their ecological services. It also synthesizes the latest knowledge and discusses the challenging issues of aquatic weed management and their control measures directed to the sustainable management of the aquatic resources.     

Potentials for exploiting allelopathy to enhance crop production

Strategies for utilizing allelopathy as an aid in crop production include both avoidance and application protocols. There are immediate opportunities for management of weed and crop residues, tillage practices, and crop sequences to minimize crop losses from allelopathy and also to use allelopathic crops for weed control. Varieties of grain and forage sorghums (Sorghum Spp.), sunflower (Helianthus annuus L.), oats (Avena sativa L.), wheat (Triticum sativum L.),rye (Secale cereale L.), and others may provide weed control and in some instances crop stimulation from their residues. Our four-year field study with cultivated sunflower resulted in no differences in weed biomass between plots with and without herbicide (EPTC) applications. Strip cropping that included sorghum showed that in the subsequent year weed density and biomass were significantly lower in the previous-year sorghum than in soybean strips. Possibilities exist for modification of crop plant metabolism to alter production of allelochemicals. Allelochemical-environmental interactions must be considered in efforts to benefit from allelopathy. Under greenhouse conditions, joint application of low levels of atrazine, trifluralin, alachlor, or cinmethylin with a phenolic allelochemical showed that these two categories of inhibitors acted in concert to reduce plant growth. Allelochemicals may also be adapted as yield stimulants or environmentally sound herbicides, such as cinmethylin and methoxyphenone. Isolation of bialophos, tentoxin, and others shows that bacteria and fungi are good sources of biologically active compounds.