241,087 research outputs found

    Morphological transformation of the old city of Beijing after 1949

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    The old city of Beijing has been recognized as the greatest masterpiece of urban planning and urban design. However, since 1949 it has experienced extensive and fast constructions and demolitions, a large number of papers argued that physical and social structure of old city of Beijing has been fading away. In order to find a proper way to protect and redevelop the old Beijing city, it could be better to answer the questions that what is the essence of urban morphology of the Old Beijing (the city before 1950s) and further how it has been transformed during last 50 years since 1949. The paper tried to provide a whole spatial morphology of the old city of Beijing and its transformation from the perspective of space syntax, a syntactical and topological approach. Based on which, it argued syntactical representation of the Old Beijing could give the light on the dual spatial structures, both for ceremony and for everyday life. Further, it argued that the transformation of syntactical morphology of the old city of Beijing had been on the way to make the spatial configuration more intelligibility for every day life since 1949. However, the continued large scale regeneration and urban extension have begun to impair the vitality of the old city due to both weakening spatial synergy and damaging compactness

    The role of space in the emergence of conceived urban areas

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    A city is usually made up of numerous different named areas but how these areas are defined is problematic. Lynch (1961) suggests that the sense of urban areas are mainly determined by thematic continuities consisting of spatial characteristics, such as the width of street, building type, colour, texture, façade detail and so on, and also gives a hypothesis that the image of urban area could be gradually developed and conceived through the network of sequences, a sense of interconnectedness at any level or in any direction. Rossi (1984) also argues that urban areas, identified as the study areas in his book, can be defined or described by their location in the city, their imprint on the ground, their topographic limits and their physical appearance which he sees as representing a consistent mode of living, involving a whole historic process of urban growth and differentiation. Both suggest, in effect, that there might be objective correlates for concepts of name areas, but little research since has taken this idea further. Here we ask if studies of cities as spatial configurations, using the techniques of space syntax, might throw light on these questions. Are there perhaps correlates between named areas and configurational properties? The paper first reviews syntactic methods applied in the past in defining different areas. These are for the most part based on spatial properties of the area itself, rather than the properties of the context, which prima facie seems likely to be a factor in how areas are defined. A new technique is then proposed for exploring properties of the context. Each axial line is taken as the root of a graph, and the numbers of axial lines found with increasing radius from the root is calculated, and expressed as a rate of change. This rate of change value is then assigned to the original axial line and expressed through bands of colour. The results show strong areal effects, in that groups of neighbouring lines tend to have similar 2 colouring, and in many cases these suggest natural areas. However the areas defined vary with the rate of change at different radii, with larger areas being identified by large radii. This technique is applied to the central areas of Beijing and London, and the results compared to known named areas. It further visually compares the area structure sketched in the Lynch’s case study of Boston with the area structure generated from spatial configuration of Boston, as a possible first step towards a cognitive dimension. Finally, it is suggested that what is being identified through this technique is not an area boundary in the normal sense, but what we might call a fuzzy boundary arising from the relation between the configurations of space within and outside the area. It further argues that the spatial definition of urban area could be more influenced by the external structure of the area, which might be called as exogenetic effect

    Quaternions and Kudla's matching principle

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    The fuzzy boundary: the spatial definition of urban areas

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    Cities seem to have some kind of area structure, usually distinguished in terms of land use types, socio-economic variables, physical appearance or historical and culturalcharacteristics. Is there any possibility that urban areas could in general be differentiated from the spatial perspective? What is the nature of boundaries between areas in terms of space? These questions could be approached by the analysis of internal or contextual spatial structure, or the relation between the two. Most studies on area structure however had focused in the main on the internal area with a secondaryrole for the context. Is there any way in which we could give more explicit attention to the context, following the clue that had come out of the earlier studies?This paper is to try to develop spatial techniques for identifying area boundaries, and looking at their performance in both the traditional areas, such as the Central London and the Inner City of Beijing, and the new development of the London Docklands. It focuses on explicitly exploring the properties of contextual structure in the formation ofarea boundaries rather than simply the properties of internal structure. After much experimentation, a new technique was arrived at for exploring properties of the context. Each axial line or segment in the whole map is taken as the root of a graph, and the numbers of axial lines, or segments, found with increasing radius from the root is calculated, and expressed as a rate of change. This rate of change value is thenassigned to the original axial line and expressed through bands of color. The results show strong areal effects, in that groups of neighbouring lines tend to have similar coloring, and in many cases, these suggest natural areas.Through the case studies, this paper suggests that historic areas typically have what we will call fuzzy boundaries. Fuzzy boundaries arise from the way space is structured internally and how this relates to the external structure of space. Such boundaries can be effective in supporting functional differentiation of areas or the growth of areal identities and characters, but do not depend on the area being either spatially self contained or geometrically differentiated, or having clear spatial limits. It is the relation of urban areas and their further surroundings that determine fuzzy boundaries of these urban areas

    A bibliography on digital computer-aided circuit analysis and design

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    Digital computer-aided electric logic circuit analysis and design bibliograph

    Mechanism conversion process and timeliness of N2-ECBM

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    Purpose. Based on the technology by which methane drainage is strengthened under gas injection, to examine the process of gas injection and the mechanism of action. Methods. Physical simulation experiment method, using the self-built coal seam and gas injection displacement experimental device, the experiment of layered pre-compression forming coal samples under vertical stress loading conditions and under the conditions of different gas injection pressures. Findings. The experiment on N2-ECBM is a dynamic process and has time effects. In the overall process, the rate of replacement was more than 60%, and the rate of displacement was less than 40%. Originality. According to the behavior of nitrogen injection in the coalbed, an assessment of displacement effects under gas injection and a quantitative evaluation of the replacement effect were presented. In every stage of the process, the replacement effect is dominant, while the role of displacement is of secondary importance. Practical implications. The experimental results have great guiding significance for optimization of gas parameters and gas source selection for gas injection flooding in underground coal seams.Мета. Вивчити процес вприскування газу у вугільний пласт й механізм його впливу на основі технології, яка дозволяє забезпечити дренаж метану, інтенсифікований за рахунок нагнітання газу. Методика. Використано експериментальний метод фізичного моделювання: була змонтована установка з моделлю вугленосного пласта для дослідження вприскування газу з метою витіснення метану. В експерименті попередньо стиснені зразки шаруватого вугілля піддавалися вертикальному навантаженню при тисках 200 кН, аналогічних тиску вприснутого газу. Газ для ін’єкцій вимірювався контролером масової витрати з максимальною швидкістю 5 л/хв, і через монітор контролювалися миттєвий і загальний потоки. В експерименті використано антрацит вугільної шахти Хуатай. Результати. Експериментальними дослідженнями встановлено, що концентрація і об’єм метану призводять до змін тиску, витрати і часу вприскування азоту, що свідчить про те, що процес заміщення метану вугільного пласта шляхом закачування азоту залежить від часу. Доведено, що експеримент з використанням технології N2-ECBM (інтенсивного вилучення вугільного метану) – це динамічний процес, в якому фактор часу відіграє вирішальну роль. Об’єм азоту, який залишається у вугіллі й витісняє метан, можна розглядати як кількісний вклад ефекту зміщення. Виявлено, що в результаті використання даної технології, рівень заміщення метану зріс більш, ніж на 60%; а рівень його витіснення – на 40%. Наукова новизна. Вивчено ефект витіснення метану при нагнітанні азоту у вугільний пласт з урахуванням поведінки газу у вугленосній товщі, а також дана кількісна оцінка ефекту заміщення, що чинить ключовий вплив на всіх стадіях процесу, в той час як роль витіснення – другорядна. Практична значимість. Результати експериментів мають принципове значення для оптимізації параметрів газу та для вибору джерела вприскування газу у вугільні пласти.Цель. Изучить процесс впрыскивания газа в угольный пласт и механизм его воздействия на основе технологии, которая позволяет обеспечить дренаж метана, интенсифицированный за счет нагнетания газа. Методика. Использован экспериментальный метод физического моделирования: была смонтирована установка с моделью угленосного пласта для исследования впрыскивания газа с целью вытеснения метана. В эксперименте предварительно сжатые образцы слоистого угля подвергались вертикальной нагрузке при давлениях 200 кН, аналогичных давлению впрыскиваемого газа. Газ для инъекций измерялся контроллером массового расхода с максимальной скоростью 5 л/мин, и через монитор контролировались мгновенный и общий потоки. В эксперименте использован антрацит угольной шахты Хуатай. Результаты. Экспериментальными исследованиями установлено, что концентрация и объем метана приводят к изменениям давления, расхода и времени впрыска азота, что свидетельствует о том, что процесс замещения метана угольного пласта путем закачки азота зависит от времени. Доказано, что эксперимент с использованием технологии N2-ECBM (интенсивного извлечения угольного метана) – это динамический процесс, в котором фактор времени играет решающую роль. Объем азота, который остается в угле и вытесняет метан, можно рассматривать как количественный вклад эффекта смещения. Выявлено, что в результате использования данной технологии, уровень замещения метана возрос более, чем на 60%; а уровень его вытеснения – на 40%. Научная новизна. Изучен эффект вытеснения метана при нагнетании азота в угольный пласт с точки зрения поведения газа в угленосной толще, а также дана количественная оценка эффекту замещения, оказывающему ключевое влияние на всех стадиях процесса, в то время как роль вытеснения – вторична. Практическая значимость. Результаты экспериментов имеют принципиальное значение для оптимизации параметров газа и для выбора источника впрыскивания газа в угольные пласты.The authors are grateful for the financial support from the Natural Science Foundation for the Youth of China (No. 51404091) and the PhD Foundation of Henan Polytechnic University (B2015-08)

    A self-learning particle swarm optimizer for global optimization problems

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    Copyright @ 2011 IEEE. All Rights Reserved. This article was made available through the Brunel Open Access Publishing Fund.Particle swarm optimization (PSO) has been shown as an effective tool for solving global optimization problems. So far, most PSO algorithms use a single learning pattern for all particles, which means that all particles in a swarm use the same strategy. This monotonic learning pattern may cause the lack of intelligence for a particular particle, which makes it unable to deal with different complex situations. This paper presents a novel algorithm, called self-learning particle swarm optimizer (SLPSO), for global optimization problems. In SLPSO, each particle has a set of four strategies to cope with different situations in the search space. The cooperation of the four strategies is implemented by an adaptive learning framework at the individual level, which can enable a particle to choose the optimal strategy according to its own local fitness landscape. The experimental study on a set of 45 test functions and two real-world problems show that SLPSO has a superior performance in comparison with several other peer algorithms.This work was supported by the Engineering and Physical Sciences Research Council of U.K. under Grants EP/E060722/1 and EP/E060722/2

    Viscous compressible flow direct and inverse computation and illustrations

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    An algorithm for laminar and turbulent viscous compressible two dimensional flows is presented. For the application of precise boundary conditions over an arbitrary body surface, a body-fitted coordinate system is used in the physical plane. A thin-layer approximation of tne Navier-Stokes equations is introduced to keep the viscous terms relatively simple. The flow field computation is performed in the transformed plane. A factorized, implicit scheme is used to facilitate the computation. Sample calculations, for Couette flow, developing pipe flow, an isolated airflow, two dimensional compressor cascade flow, and segmental compressor blade design are presented. To a certain extent, the effective use of the direct solver depends on the user's skill in setting up the gridwork, the time step size and the choice of the artificial viscosity. The design feature of the algorithm, an iterative scheme to correct geometry for a specified surface pressure distribution, works well for subsonic flows. A more elaborate correction scheme is required in treating transonic flows where local shock waves may be involved