B 句意理解题.根据本段内容可知答案. C Charging your mobile phone might soon be as simple as taking a walk around the block. Scientists have created a new machine that harvests energy from the movement of the knees while walking. Six volunteers wore the deviceson their legs while walking on a treadmill and were able to produce about five watts of electrical power each. That’s enough energy to run 10 mobiles at the same time. “Since muscles are the powerhouses of the body, my colleagues and I designed our device to generate electricity from the move of the knee joint, said Max Donelan. “It resembles a knee brace and weighs about 1.5 kilograms including the gearing and generator. The apparatus catches the energy of a person’s movement by connecting an electrical generator to knee moving. When the wearer extends the knee, a gear on the device turns and spins the generator, which builds up energy. When the knee is flexed, the device turns off so as not to tax the wearer. The machine senses moving and knows when to activate itself. The design allows a person to use the tool without using much additional energy beyond the normal demands of walking. The researchers measured the volunteers’ oxygen intake and carbon-dioxide output to make sure it wasn’t strenuous to use. People are an excellent source of portable power. An average-sized person stores as much energy in fat as a 1,000-kilogram battery. People recharge their body batteries with food. The device could be used to power computers in remote areas where electricity is shot. The early markets are people whose lives depend on portable power, such as people with artificial limbs. On the military side, some soldiers have an extreme dependence on batteries these days, so both these groups could benefit. 【查看更多】
