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While research has tackled the hub-and-spoke network design problem, that research has overlooked the air-truck modal integration issue which is a common feature of real express delivery systems. This paper devises integer linear programs to represent the mode and route assignment aspects of the operational problem. The model is solved under four different levels of delivery schedule, and the results show that as the promised delivery schedule is relaxed, not only does the use of truck routes become more desirable, but also interesting adjustments in mode and hub assignment occur. Consider the case of hubs in Los Angeles and Dayton. As the time constraints are relaxed, cities such as Minneapolis and New Orleans originally linked by air to Los Angeles, switch to Dayton because cheaper truck routes become feasible. 相似文献
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北宋时期,朝廷在淮南地区运河沿岸州军设置转般仓,这些州军具有了转般粮食物资进京的功能;又先后置发运司于真州和泗州,使其开始具有总管东南漕运事务的职能;盐利也集中于此,同时亦掌控着地方物资的上供经费.其他物资转输区域则经常出现改变转运方式的情形,中转区域改变了起始区域输出物资的运输方式,减轻了部分运输成本.起始区域在加重中转区域负担的同时,亦对中转区域的经济繁荣有促进作用. 相似文献
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Yong Ge Can Wang Xiujia Huan Su-chiu Kuo Hsiao-chun Hung Zhenhua Deng 《Archaeometry》2023,65(6):1313-1321
The selection of a non-shattering phenotype is a pivotal change in the process of rice domestication. However, current research is heavily restricted by the preservation conditions of macro-plant remains in early and middle Neolithic sites, as very limited well-preserved rice spikelet bases could be retrieved. We present a non-destructive method based on micro-computed tomographic (CT) scanning, which could provide detailed visualization of the internal structures of charred spikelet bases and efficiently discriminate the shattering and non-shattering phenotypes of rice spikelet bases according to the abundance of fusiform echinate phytoliths. It could be widely applied in different contexts, especially those poorly preserved specimens and tempers in pottery sherds, greatly improving our knowledge of rice domestication. 相似文献
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Xiao Yong 《中国西藏(英文版)》2018,(3)
正The cold season isjust about to arrive in Lhasa.A tallllbetan man is standing upon the golden roof of the Jokhang Temple to look out into distance.His name is Tsegya,a man with a deep affection for this very roof.This is the place where his karma connects him to his produced mandalas.Tsegya told me that 相似文献
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明朝初年,国脉皆仰东南,为解决南方粮财物的北运问题,宋礼和白英受命组织修建了大运河山东段南旺分水枢纽。该枢纽主要包括引汶济运、导泉补源、设立水柜和置闸节流四个组成部分。其中,引汶济运是工程之重点,包括戴村坝、小汶河、南旺分水以及配套工程等四个子系统。这些水利设施组成一个和谐的系统工程,保证了该段运河的水量稳定充足,从而实现了大运河500余年的正常通行。南旺分水枢纽代表了我国古代运河水工的最高科学技术成就,堪称世界水利史上的一大经典范例。 相似文献
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真人元开(Omino Mihune)撰于779年的鉴真传记<唐大和上东征传>,有多种写本、刊本传世.1762年以后的刊本,流传颇广,其对文本的字词误读甚至影响到今天.本稿依据现存日本的古写本及多种刊本,对鉴真第二次东渡携带品的误读进行辨析、纠谬,指出在研究域外汉籍中写本的重要性. 相似文献
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援藏工作是中央政府支援帮助西藏实现跨越式发展的重要方式与途径。西藏和平解放后,中央政府制定了一系列特殊政策和措施,帮助和扶持西藏发展,并动员和组织内地发达地区支援西藏建设。20世纪80年代,中央把立足民族平等、加快西藏发展作为民族工作的重点。1984年中央第二次西藏工作座谈会后,国家对西藏经济支持力度逐年增大,全国性的援藏工程开始。 相似文献
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Yong Yi Zhen Guangxu Wang Ian G. Percival 《Alcheringa: An Australasian Journal of Paleontology》2017,41(2):141-168
Zhen, Y.Y., Wang, G.X. &; Percival, I.G., August 2016. Conodonts and tabulate corals from the Upper Ordovician Angullong Formation of central New South Wales, Australia. Alcheringa 41, xxx–xxx. ISSN 0311-5518.The Angullong Formation is the youngest Ordovician unit exposed in the Cliefden Caves area of central New South Wales. Its maximum age is constrained by a Styracograptus uncinatus graptolite Biozone fauna at the very top of the underlying Malongulli Formation, but the few fossils previously reported from higher in the Angullong Formation are either long-ranging or poorly known. From allochthonous limestone clasts in the middle part of the formation, we document a conodont fauna comprising Aphelognathus grandis, A. solidum, Aphelognathus sp., Aphelognathus? sp., Belodina confluens, Drepanoistodus suberectus, Panderodus gracilis, Panderodus sp., Phragmodus undatus, Pseudobelodina inclinata and Pseudobelodina? sp. aff. P. obtusa, which supports correlation with the Aphelognathus grandis Biozone (late Katian) of the North American Midcontinent succession. The species concepts of Aphelognathus and Pseudobelodina are reviewed in detail. Associated corals are exclusively tabulates, dominated by agetolitids, including Agetolites angullongensis sp. nov., Heliolites orientalis, Hemiagetolites breviseptatus, Hemiagetolites sp. cf. H. spinimarginatus, Navoites sp. cf. N. circumflexa, Plasmoporella bacilliforma, P. marginata, Quepora sp. cf. Q. calamus and Sarcinula sp. Affinities of the coral fauna from the Angullong Formation are closer to faunas from northern NSW and northern Queensland than to the locally recognized Fauna III of late Eastonian age in central NSW. We propose a subdivision of Fauna III to account for this difference, with the late Katian Fauna IIIB characterized by the incoming of agetolitid corals. The currently known distribution of representatives of this group with adequate age constraints suggests that agetolitids possibly originated in North China, subsequently migrating to Tarim, South China and adjacent peri-Gondwanan terranes while also spreading eastward to northern Gondwana, where they progressively moved through eastern Australia to reach the central NSW region by the early Bolindian.Yong Yi Zhen* (yong-yi. zhen@industry. nsw. gov. au) and Ian G. Percival (ian. percival@industry. nsw. gov. au), Geological Survey of New South Wales, W.B. Clarke Geoscience Centre, 947–953 Londonderry Road, Londonderry, NSW 2753, Australia; Guangxu Wang (gxwang@nigpas. ac. cn), State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road Nanjing 210008 PR China. 相似文献