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Spacecraft flew hundreds of thousands to hundreds of millions of kilometers from the earth, injecting speed when the size and direction of a slight error, arrived at target planets will appear large deviation error, for example, when Mars probe injecting speed 1 m/s speed (about one over ten thousand), arrived at Mars, about 100000 km distance deviation. Therefore, precise control and navigation must be carried out during the long flight. Flying to the moon is usually controlled by the orbital control system of the ground and space probe (see orbit control). Interplanetary flight distances, radio signal transmission time is long, the real-time remote control, can't so planets and interplanetary spacecraft orbit control system shall have the ability of autonomous navigation (see interstellar travel navigation and control). The United States, for example, "pirates" spacecraft in space flight of more than eight hundred million km, for 11 months of 2000 times of autonomous orbit adjustment, the final surface to achieve a soft landing on Mars, placement accuracy up to 50 km. In addition, in order to ensure the accuracy of the orbit control engine, the communication antenna is always aimed at the earth, and other systems work normally, and the detector has the autonomous attitude control ability
1. Safety reversal: All the garage door opener designed with safety reversal feature. The door has two sensors situated six inches over the floor level, each side with the door. When any object like pet, child or some different, call light beam developed by sensor whilst the door is closing, the door stops and reverses. If your opener haven't this safety reversal feature, put it back as soon as possible.
The world intellectual property organization in 1977 edition of the licensing handbook "for developing countries to use, to the definition of technology:" technology is knowledge for the manufacture of a product system, the adoption of a process or provide a service, regardless of whether this knowledge is reflected in an invention, a shape design, a utility model, or a kind of new plant varieties, or reflected in technical information or skills, or reflected in the expert for the design, installation, run a factory or maintenance or for managing a business or its activities and provide services or assistance, etc." This is by far the most comprehensive and complete definition of technology in the world. In fact, the intellectual property organization defines all the scientific knowledge that can bring economic benefits to the world as technology
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