Terrain-Specific: Contemporary Landscape Architecture in Canada

The Canadian landscape has typically captured a global imaginary of a pristine wild, but how might its urban designed landscapes be distinctly understood? Foregrounded by the landscape transformations accelerated by climate change, the book Innate Terrain: Canadian Landscape Architecture, edited by Professor Alissa North from the University of Toronto, highlights landscape architecture projects situated on the unique Canadian terrain. Providing further provocation on Canadian landscape architecture, Innate Terrain seeks to fill the literary gap on contemporary landscape perspectives, distinguishing Canadian landscape architecture from global practice, and particularly, its well-documented American counterpart. Landscape architecture in the Canadian context has evolved and established its own distinct identity, one imbued with national and local sensitivities. Informed by diverse environmental and cultural contexts, Canadian-designed landscapes reflect and refer to the prevailing ecosystems of Canada’s innate terrain. Contrary to the preceding International Style, landscape architecture projects in Canada have adopted the ethos of Critical Regionalism in the second half of the 20th century. Contemporary Canadian practitioners are designing landscapes that are deeply informed by their surrounding geographical context while emphasizing cultural specificity. Central to this cultural specificity, addressed by a new generation of landscape architects, is the increasing recognition of Indigenous Traditional Knowledge within the discipline. Canadian landscape architects have collaborated with First Nations, Inuit, and Métis communities, including the keepers of this knowledge, to develop land management strategies and design landscape interventions.     

A unified critical state model for geomaterials with an application to tunnelling

This paper is prepared in honour of Professor E.T. Brown for his outstanding contributions to rock mechanics and geotechnical engineering and also for his personal influence on the first author's research career in geomechanics and geotechnical engineering. As a result, we have picked a topic that reflects two key research areas in which Professor E.T. Brown has made seminal contributions over a long and distinguished career. These two areas are concerned with the application of the critical state concept to modelling geomaterials and the analysis of underground excavation or tunnelling in geomaterials.Partially due to Professor Brown's influence, the first author has also been conducting research in these two areas over many years. In particular, this paper aims to describe briefly the development of a unified critical state model for geomaterials together with an application to cavity contraction problems and tunnelling in soils.     

A probabilistic load shedding concept considering highly volatile local generation

Automatic load shedding is the ultimate countermeasure against imbalance in a power system and can effectively help preventing large blackouts. Taking into account a high penetration of renewable energy sources (RES) in the distribution grid, a clear distinction between load and generation at the PCC becomes increasingly more difficult. For that reason an adaptation of frequency relay parameters and their locations of installation are necessary. In Europe this is rest on a multi-step plan based on values such as the yearly peak load. In this paper a novel probabilistic method for automatic load shedding is presented that uses the average values instead of peak values for load shedding. Its applicability is verified by a dynamic power system model that was developed to compare the classical and novel probabilistic load shedding principle. The method is verified using data from a German TSO.     

基于振动实测的非均质地层钻头失效分析与对策

四川盆地作为国内页岩气开发的重点区域,通过近几年的不断攻关和实践,机械钻速得到了提高,但由于受地层复杂、可钻性差、非均质性强等地质因素的影响,导致井下钻柱系统不良振动剧烈,容易出现钻头损坏严重、钻速较低等问题,严重影响了钻井时效。为了解决上述难题,以该盆地涪陵工区上二叠统龙潭组—中二叠统茅口组为例,采用井下振动高频测量工具的实测手段,测量了钻头—钻柱系统的动态振动加速度参数,结合地层的岩性和矿物组分分析,研究钻头失效原因与对策,并开展了现场试验。研究结果表明:①在非均质地层中钻进的钻头—钻柱系统产生了大于40 m/s~2的高幅值瞬时冲击振动,高幅值的瞬时冲击是导致钻头先期失效的主要原因;②提出了抑制高幅值的瞬时冲击振动采用"减振+增压"工具组合和避免井下工具共振的钻井参数;③采用钻井新参数的试验井比邻井的高幅值瞬时振动降低了17%,单只钻头进尺增加24%,钻头工作环境得到了较大的改善,钻头使用数量减少。结论认为,该研究成果能够有效地改善钻头—钻柱系统的振动状态,有利于达成延长钻头使用寿命的目标。     

对成油体系临界时刻的思考

在分析Magoon和Dow对临界时刻研究的基础上 ,从事件持续时间的长短对油气最终生成的影响这一角度 ,通过对成油体系中各事件发生的过程进行分析 ,指出原成油体系事件分析图表的不合理之处 ;建立成油体系临界时刻分析模型 ,探索临界时刻定量评价的方法以及方法在油气潜力评估中的应用意义     

大功率晶体管的保护电路

大功率晶体管调速系统中作为开关元件使用时，共优点是开关频率比可控硅的高，但是不注意保护就容易损坏。着重研究过电流故障，并对保护作用的影响进行了分析，进而提出了防止过电流的方法和工作原理。     

Fast determination of critical eluent composition for polymers by gradient chromatography

Gradient chromatography was applied in order to calculate the composition at elution for different methacrylates on normal phase columns. In addition the composition at elution was determined for polyethyleneoxide on a reverse phase column. It is shown that high molar mass polymers elute for a given homopolymer irrespective of their molar mass at the same eluent composition, which varies only slightly with gradient slope. In general the composition at elution in gradient chromatography is expected to be slightly lower than the true critical composition. For high molar mass polymers we found this composition to be close to the critical composition determined by isocratic experiments. The difference between the composition at elution and the true critical composition for a variety of polymethacrylates and for polyethyleneglycol was found to be only between 0.2 and 5%. Thus, after estimating the composition at elution, only a small number of additional isocratic experiments is needed to find the exact critical composition.     

Structural and Superconducting Property Variations with Nominal Mg Non‐Stoichiometry in MgxB2 and Its Enhancement of Upper Critical Field

By applying a combination of characterisation tools, changes in structural and superconducting properties with nominal Mg non‐stoichiometry in Mg_xB₂ are found. The non‐stoichiometry produces enhanced in‐field critical current densities (J_c's) and upper critical field / irreversibility field (H_c2/H_irr(T)) values. Upper critical fields of ～ 21 T (4.2 K) were obtained in nominal Mg‐deficient samples compared to ～ 17 T (4.2 K) for near‐stoichiometric samples.     

Ability of a contactless inductive device for the characterization of the critical current versus temperature in superconducting rings at temperatures close to TC

Critical current measurements for three polycrystalline rings of YBCO, three Bi-2223, and one YBCO + Ag were developed from a temperature close to 80 K to the critical temperature using a previously reported contactless inductive device based on the transformer method. These data were used to analyze the ability of this device to characterize, in superconducting rings, the Ginzburg-Landau, Ambegaokar-Baratoff, and De Gennes regimes as well as the crossover temperature between them.     

Critical heat flux on a flat plate heater located at the middle of a duct in forced flow of pressurized He II

Critical heat fluxes (CHFs) were measured for two types of rectangular ducts containing horizontal flat plate heaters. One has the flat plate heater of 6 mm wide and 20 mm long located on the inner lower wall at 50 mm from the inlet. The other duct has two horizontal flat plates of 6 mm wide and 20 mm long on inner upper and lower walls at 50 mm from the inlet. The equation of CHF for the forced convection containing a new nondimensional-parameter m introduced in order to calculate cross-sectionally averaged liquid temperature at the center of the duct was derived based on two fluid model, ordinary convection theorem and experimental results. It was confirmed that this correlation can describe not only the author's data on the duct but also other worker's data for channels with different shapes and sizes.