日本对外贸易的基本情况

<正> 一、日本商社在对外贸易中的作用日本现有8,661家贸易商社,其中股票在证券市场上市的有146家,包括9家大综合商社和137家专业骨干企业。日本九大综合商社为:丸红、三菱商事、三井物产、伊藤忠、住友商事、东棉、兼松江商、日棉、日商岩井。1987年,这九大综合商社的总销售额为90兆日元,占日本全国总销售额的30.2％。在进出口贸易方面,九大综合商社的出口额为968亿美元,占日本出口总额的45.1％;进口额为

Multipath and interference effects in secondary surveillance radar systems

Secondary surveillance radar (SSR) offers many advantages for air traffic control (ATC) compared to normal (or primary) radar including substantially lower cost and improved performance. Because of the increasing reliance being placed on SSR by ATC a number of the system problems associated with, SSR are becoming less casily tolerated. The Paper discusses these problems, which mainly arise from multipath and mutual interference effects, and proposes solutions.