太阳能路灯的灯杆顶端是太阳能电池板，它能将太阳能转化为电能，并向灯杆下方的蓄电池充电，将电能转化为       能储存起来，供夜晚路灯照明．若在一定时间内，太阳光辐射到该太阳能电池板的能量为2.7×10⁷J，这与完全燃烧       kg的煤放出的热量相当；这些能量经转化后，可供功率为35W的路灯工作60h，那么该太阳能路灯的能量转化效率是      %（煤的热值为3.0×10⁷J/kg）．

For more than two centuries, American’s colleges and universities have been the backbone of the country’s progress. They have educated the technical, managerial, (1) and provided generation after generation of national leaders. Today educators from around the globe are turning to U. S. institutions of higher learning (2) . They are apt to find many reasons for the excellence of American universities, but (3) stand out as watersheds:
Education (4) : In 1862 Congress enacted the Land-Grant College Act, which essentially extended the opportunity of higher education (5) , including such disenfranchised groups as women and minorities. Each state was permitted to sell large tracts of (6) and use the proceeds to endow at least one public college.
(7) : Over the years, the decentralization and diversity of the America’s colleges and universities have promoted competition for students and resources. Competitive pressure first arose (8) . The academy’s impact really grew after World War II, when (9) commissioned by President Roosevelt argued that it was the federal government’s responsibility to (10) for basic research. Instead of being centralized in government laboratories, scientific research (11) in American universities and generated increasing investment. It also gave graduate students research opportunities and helped (12) far and wide, to the benefit of industry, medicine and society as a whole.
(13) : The end of the World War II saw passage of the Servicemen’s Readjustment Act of 1944. The law, which provided for (14) for returning veterans, made an already democratic higher-education system accessible in ways that were (15) in Europe, opening the doors of the best universities to men and women who had (16) of going to college.
(17) : The creation of federal loan guarantees and subsidy programs, as well as outright grants for college students brought (18) to higher education and further helped to democratize access. Since its founding (19) , the Federal Family Education Loan Program has funded more than 74 million student loans worth more than (20) .