【正文】 Baumgartner the disappointing news: Mission aborted. r plays an important role in this mission. Starting at the ground, conditions have to be very calm winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our daytoday weather lives. It will climb higher than the tip of Mount Everest ( miles/ kilometers), drifting even higher than the cruising altitude of mercial airliners ( miles/ kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause),e can expect a lot of turbulence. The supersonic descent could happen as early as Sunda. The weatheThe balloon will slowly drift to the edge of space at 120,000 feet ( Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform. Below, the Earth bees the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, he39。嫌惡過自己的怯懦，最終卻發(fā)現(xiàn)有很多 緣分 ，有很多錯(cuò)過，好像冥冥之中真的已經(jīng)注定。 Then in high school, think don39。s plaint. In a statement the Russian side added: We found no racist insults from fans of CSKA. Age has reached the end of the beginning of a word. May be guilty in his seems to passing a lot of different life became the appearance of the same day。re clear about the terms of the agreement. It might be best to get advice from an experienced adviser, for example, at a Citizens Advice Bureau. To find your nearest CAB, including those that give advice by , click on nearest CAB. For more information about making a claim to an employment tribunal, see Employment tribunals. The (lack of) air up there Watch mCayman Islandsbased Webb, the head of Fifa39。 感謝院系領(lǐng)導(dǎo)和我的師長們耐心指點(diǎn)和思想上給我的啟發(fā) ，感謝網(wǎng)站提供有關(guān)資料和所有與我交流探討的同學(xué)和朋友。 } } 重慶科技學(xué)院高等教育自學(xué)考試本科畢業(yè)論文 畢業(yè)設(shè)計(jì)（論文） 19 結(jié)束語 本文所設(shè)計(jì)的基于 AT89C51 單片機(jī)倒車防撞報(bào)警系統(tǒng)是保障汽車倒車安全的輔助系統(tǒng)，通過超聲波探頭發(fā)出超聲波，使用高速單片機(jī)測量車與障礙物之間的往返時(shí)間然后再計(jì)算車與障礙物之間的距離，并加入了軟件補(bǔ)償，提高了距離計(jì)算的精度，然后顯示在 1602 液晶上。 //開總中斷 // ET0=1。 } TR0=1。 //清屏 Write_（ 0 80）； For(c=0。a16。 _nop_()。 Icden=0； //將使能端置 0 為了 完成高脈沖 } /********************************************/ 1602 液晶寫數(shù)據(jù)函數(shù) /********************************************/ Void write_date() } While(Icd_busy90)。 //使能端置低電平 P0=； //將要寫的命令字送到數(shù)據(jù)總線上 _nop_()。 _nop_()。 Lcd_busy 為 0 時(shí)，閑，可寫指令與數(shù)據(jù)。 write_date(0 30＋ num1)。 Num0=distance%10。 time=(TH0*256+TL0)/2。 _nop_()。 _nop_()。 超聲波發(fā)射程序 Void send() { csb_in=1； for(i=0。 ：該腳與地之間連接檢波電容，電容量大為平均值檢波，瞬間相應(yīng)靈敏度低；若容量小 ，則為峰值檢波，瞬間相應(yīng)靈敏度高，但檢波輸出脈沖寬度變動(dòng)大，易造成誤動(dòng)作，推薦參數(shù)為 f?？删幊檀?UART 通道 4K 字節(jié)可重擦寫 Flash 閃速存儲器 圖 是電路中選用的發(fā)射傳感器的指向圖。因此， 超聲波接收傳感器具有很好的頻率選擇特性。 超聲波發(fā)生器內(nèi)部結(jié)構(gòu)有兩個(gè)壓電晶片和一個(gè)共振板。在空氣中傳播超聲波，其頻率較低，一般為幾十 KHz，而在固體、液體中則頻率可用得較高。超聲波傳感器有發(fā)送器和接收器，但一個(gè)超聲波傳感器也可具有發(fā)送和接收聲波的雙重作用。 關(guān)鍵詞 ： 單片機(jī) 超聲波 AT89C51 重慶科技學(xué)院高等教育自學(xué)考試本科畢業(yè)論文 畢業(yè)設(shè)計(jì)（論文） Abstract With the development of society and economy of transportation industry is booming, the number of cars in the sharp rise. Traffic congestion has bee more and more serious, the crash occurred repeatedly, resulting from the inevitable casualty and economic loss, in view of this situation, design a kind of fast response, high reliability and more economy car collision avoidance warning system to be imperative, ultrasonic ranging method is the most mon type of distance measuring method, this paper describes the use of ultrasonic locating design a backdraft anticollision alarm system. The content of the thesis is based on the AT89C51 singlechip integration, design based on AT89C51 backdraft anticollision alarm system. The system uses a bination of hardware and software, the method of module, and multiuse characteristics. This paper summarizes the development and basic principle of ultrasonic detection, introduces the principle and characteristics of ultrasonic sensor. Some of the main parameters for the system were discussed, and introducing ultrasonic ranging system functions basis, the overall position of the system, through a variety of transmitting and receiving circuit design parison, the best design scheme, and various system design unit this paper introduces the principle of. On the position of the system circuit chip are introduced, and elaborated the principles of their work. This paper introduces the software structure of system, programmed to realize the function of the system. Finally, through the analysis of system error, an improved scheme is presented. Key words: single chip ultrasonic AT89C51 重慶科技學(xué)院高等教育自學(xué)考試本科畢業(yè)論文 畢業(yè)設(shè)計(jì)（論文） 目 錄 1超聲檢測發(fā)展綜述 ......................................................................................................... 1 2 超聲波介紹