Trialling tools using hand-weeding,weed mat and artificial shading to control nuisance macrophyte growth at multiple scales in small agricultural waterways

ABSTRACT

Introduced aquatic macrophytes can dominate small agricultural waterways in summer and autumn becoming a significant management problem. Excessive growth can clog waterways, causing drainage issues and reducing agricultural productivity while in-stream velocities are reduced and sedimentation increased. Consequently, water managers remove them by mechanical clearance, chemical spray and cutting which can be costly and have negative impacts on in-stream habitat and ecological health. We trialled three tools to reduce macrophytes: hand-weeding, weed mat and artificial shading, at a reach-scale (50?m) and larger-scale (200–400?m). Hand-weeding reduced cover in the short-term, however macrophytes recovered to pre-treatment levels within one season. Weed mat along the banks was effective at reducing emergent macrophytes, particularly Erythranthe guttata (monkey musk) and Nasturtium microphyllum (watercress). Weed mat lasted for several growing seasons and continued to be effective. Shading over the waterway using polythene markedly reduced submerged macrophytes indicating that heavy shading by riparian plantings could reduce submerged macrophytes in the longer-term. These results indicate that in the short-term, weed mat could be used to limit sprawling emergent macrophytes. In the longer-term, weed mat used in conjunction with riparian planting could provide shading so that macrophyte cover in these small waterways could be reduced and controlled.     

基于Mohr-Coulomb准则的黏弹-塑性海冰动力学本构模型

针对中小尺度下海冰动力作用过程中的漂移、重叠和堆积特征,在连续介质力学基础上建立了一个黏弹塑性海冰动力学本构模型.该模型主要包括四部分,即海冰在屈服前的Kelvin Vogit黏弹模型、海冰塑性屈服的Mohr Coulomb准则、屈服后相关联的正交流动法则和影响海冰强度的静水压力.采用黏弹塑性本构模型对规则海域内的海冰堆积过程进行了数值试验,其结果与传统黏塑性模型、改进的黏塑性模型和经典冰坝理论的解析解相符,可合理地模拟海冰堆积的动力过程.为进一步检验该黏弹塑性本构模型的适用性,对渤海海冰的动力过程进行了48h的数值模拟,计算结果与海冰卫星遥感现场观测资料一致.通过与传统的黏塑性和改进的黏塑性模型结果的对比分析,进一步验证了黏弹塑性模型在中小尺度海冰动力学模拟中的可靠性.在以上海冰堆积的数值试验和渤海海冰动力学模拟中均采用了光滑质点流体动力学(SPH)方法.     

Gender performances in a service orientated workplace in Aotearoa/New Zealand

Abstract:  This paper uses Butler's (1990) concept of performativity to explore the constructions of feminine and masculine identities integral to the gendered bodily performance in 'interactive' service economies. The empirical research for this paper is based on Fat Freddie's student pub in Aotearoa/New Zealand, and was collected over an eight-week period using an ethnographic methodology. While Butler argues we 'do' gender, I explore how these 'fabrications' are naturalized, and the effect this has on the division of labour within Fat Freddie's. While these performances are regulatory, they are, however, unstable and alternate subject positionings can be adopted. I discuss how these subject positionings within Fat Freddie's can disrupt dichotomized gendered divisions and hegemonic understandings of appropriate gendered roles and identities.     

A viscoelastic-plastic constitutive model with Mohr-Coulomb yielding criterion for sea ice dynamics

A new viscoelastic-plastic （VEP） constitutive model for sea ice dynamics was developed based on continuum mechanics. This model consists of four components： Kelvin-Vogit viscoelastic model, Mohr-Coulomb yielding criterion, associated normality flow rule for plastic rehololgy, and hydrostatic pressure. The numerical simulations for ice motion in an idealized rectangular basin were made using smoothed particle hydrodynamics （SPH） method, and compared with the analytical solution as well as those based on the modified viscous plastic（VP） model and static ice jam theory. These simulations show that the new VEP model can simulate ice dynamics accurately. The new constitutive model was further applied to simulate ice dynamics of the Bohai Sea and compared with the traditional VP, and modified VP models. The results of the VEP model are compared better with the satellite remote images, and the simulated ice conditions in the JZ20-2 oil platform area were more reasonable.     

Middle Pleistocene environments,landscapes and tephrostratigraphy of the Armenian Highlands: evidence from Bird Farm 1, Hrazdan Valley

The significance of the southern Caucasus in understanding Pleistocene hominin expansions is well established. However, the palaeoenvironments in which Palaeolithic occupation of the region took place are presently poorly defined. The Hrazdan river valley, Armenian Highlands, contains a rich Palaeolithic record alongside Middle Pleistocene volcanic, fluvial and lacustrine strata, and thus offer exciting potential for palaeoenvironmental reconstruction. We present the first results of sedimentological, geochemical, tephrostratigraphical and biological (diatoms) study of the sequence of Bird Farm 1, located in the central part of the valley. These data show six phases of landscape development during the interval 440–200 ka. The sequence represents the first quantitative Pleistocene diatom record from the Armenian Highlands and the southern Caucasus, and indicates the persistence of a deep, stratified lacustrine system, with evidence for changing lake productivity that is tentatively linked to climate. Furthermore, major element chemical characterization of visible and crypto-tephra horizons in the sequence enables the first stages of the development of a regional tephrostratigraphy. Together, the evidence from Bird Farm 1 demonstrates the importance of lacustrine archives in the region for palaeoenvironmental reconstruction and highlights the potential for linkages between archives on both a local and regional scale.