Auctions (拍卖) are public sales of goods, conducted by an officially approved auctioneer. He asked the crowd to gather in the auction room to bid (出价,喊价) for the various items on sale. He encourages buyers to bid higher figures, and finally names the highest bidder as the buyer of the goods. This is called "knocking down" the goods, for the bidding ends when the auctioneer bangs a small hammer on a raised platform.The ancient Romans probably invented sales by auction, and the English word comes from the Latin "auction", meaning "increase". The Romans usually sold in this way the spoils taken in war; these sales were called "sub hasta", meaning "under the spear (矛)", a spear being stuck in the ground as a signal for a crowd to gather. In England in the eighteenth and nineteenth centuries goods were often sold "by the candle"; a short candle was lit by the auctioneer, and bids could be made while it was burning.Practically all goods can be sold by auction. Among these are coffee, skins, wool, tea, cocoa, furs, fruit, vegetables and wines. Auction sales are also usual for land and property, antique furniture, pictures, rare books, old china and works of art. The auction rooms at Christie’s and Sotheby’s in London and New York are world famous.An auction is usually advertised beforehand with full particulars(细节)of the articles to be sold and where when they can be viewed by the buyers. If the advertisement cannot give full details, catalogues are printed, and each group of goods to be sold together called a "lot", is usually given a number. The auctioneer need not begin with Lot One and continue the numerical order, he may wait until he notices the fact that certain buyers are in the room and then produce the lots they are likely to be interested in. The auctioneer’s services are paid for in the form of a percentage of the price the goods are sold for. The auctioneer therefore has a direct interest in pushing up the bidding. Auctioned goods are sold()
A. for the highest price offered
B. at fixed prices
C. at prices lower than their true value
D. at prices offered by the auctioneer
轴的结构设计时,要考虑轴上零件的合理布置,及固定方式;轴承类型及位置。轴上作用力的大小及分布、轴的( )等,来合理确定轴的结构。以保证轴上的零件定位准确,固定可靠、拆装方便。是轴的结构尽量,尽量减小应力集中。
A. 使用性能要求
B. 受力形式
C. 配合性质
D. 加工工艺及装配工艺