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基于GIS的合肥市BRT和Metro的交通可达性研究-part1

相对传统公交, BRT和Metro系统作为一种新型的公共交通方式,是一个涉及面广、影响因素多、相对灵活的体系。BRT通过对传统公共汽车在规划、设计、运营和管理上的改良,从而以较少的投资、较强的灵活性实现较高的服务效率;Metro在地下,不占用地面土地,运行速度快,载客容量大,大大的减少居民出行时间。BRT和Metro系统规划的核心问题,在于如何与城市自身特点紧密配合,寻求快速公交和地铁与其它城市公共交通方式之间的合理结构模式,建立一体化的城市交通系统。因此,在快速公交和地铁系统决策的过程中,必须坚持整体化的规划原则与方法,对快速公交和地铁系统的规划、实施、运营、优化这一不断推进的过程进行全面分析。因此我们对BRT和Metro路线系统对合肥市中心城区可达性影响的分析。

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在程序中时间旅行

三年前,当我写下那篇青涩的『永恒不变的魅力』的文章时,我刚刚是 elixir 和 clojure 的入门者。我如饥似渴地从 Bret Victor,Rich Hickey 等人身上吸取思想和力量,来浇筑我对函数式编程的信仰。函数式编程语言中有诸多让人赞不绝口的设计思想,但 immutability(不可变)显然是皇冠上的明珠。它让我们可以肆无忌惮地使用并发,不必考虑 lock,因为没有 critical section 可言;它让我们不必再终日在野指针造成的 segment fault,坏引用导致的 exception 中彷徨哀怨甚至自戕。当我们用一个产品的时候,确定性让我们感到安全和愉悦 —— 你使用微信,发给朋友的信息如果代表发送的小菊花停了没有惊叹号,那就一定成功了,这就是确定性;immutable 给程序员带来的确定性是:我给你一个引用,只要你拿着,就算到了天荒地老,海枯石烂它也能够访问,且还守候着原来的值。

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Google Earth Engine——全球摩擦面列举了北纬85度和南纬60度之间的所有陆地像素在2015年的名义年的陆地迁移速度。

This global friction surface enumerates land-based travel speed for all land pixels between 85 degrees north and 60 degrees south for a nominal year 2015. This map was produced through a collaboration between the University of Oxford Malaria Atlas Project (MAP), Google, the European Union Joint Research Centre (JRC), and the University of Twente, Netherlands. The underlying datasets used to produce the map include roads (comprising the first ever global-scale use of Open Street Map and Google roads datasets), railways, rivers, lakes, oceans, topographic conditions (slope and elevation), landcover types, and national borders. These datasets were each allocated a speed or speeds of travel in terms of time to cross each pixel of that type. The datasets were then combined to produce this “friction surface”, a map where every pixel is allocated a nominal overall speed of travel based on the types occurring within that pixel, with the fastest travel mode intersecting the pixel being used to determine the speed of travel in that pixel (with some exceptions such as national boundaries, which have the effect of imposing a travel time penalty). This map represents the travel speed from this allocation process, expressed in units of minutes required to travel one meter. It forms the underlying dataset behind the global accessibility map described in the referenced paper.

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