“No man is an island，”wrote the poet John Donne several centuries ago.He was acknowledging one of our most distinctive characteristics：the fact that we are social animals whose behavior and personalities are shaped by the groups to which we belong.
Throughout life，most of our daily activities are performed in the company of others.Whether our purpose is working，playing，raising a family，learning，or simply relaxing，we usually pursue it in groups，even if the group is as small as two or three people.Out need for human contacts is not merely a practical one；it is a deep psychological need as well.If people are deprived of the company of others for prolonged periods，mental breakdown is the usual result.Even the Geneva Convention（日内瓦公约），an international agreement that regulates the treatment of prisoners of war，recognizes this need.It regards solitary（孤独的）imprisonment for more than thirty day as a cruel form of torture（折磨）.
In its strictest sense，a group is a collection of people interacting together in an orderly way on the basis of shared expectations about one another’s behavior.As result of this interaction，members feel a common sense of “belonging.”They distinguish members from nonmembers and expect certain kinds of behavior from outsiders.

假设一个磁盘有200个磁道，编号从0～199。当前磁头正在143道上服务，并且刚刚完成了125道的请求。如果寻道请求队列的顺序是86，147，91，177，94，150，102，175，130

For anyone who hates doing yard work，your new best friend may have arrived.A robot can autonomously shovel snow，collect leaves and cut grass.
“We’re trying to help people not spend time on yard work，”said Steven Waelbers，the designer of the robot.“We want people to enjoy their free time with their family.”
The electric robot can run by itself in right directions with the help of two beacons （信号塔）that must be placed in the yard.The robot includes a camera and ultrasound sensor （超声传感器）that Waelbers said would stop quickly when it finds pets and people.
Owners of the robot will need to regulate the values stored in the robot.Then it will confirm the task it’s going to take.Before the robot operates by itself，an owner must manually wheel it around the yard –taking it around any obstacles like trees，bushes or mailboxes.By doing this，the robot is taught how long and wide the lawn is，and won’t accidentally destroy your rose bush or run to the neighborhood.
Once this setup is complete，and the $3，999robot has been trained on where to cut grass，rake leaves and shovel snow，it operates without any supervision.
Waelbers has always loved to build robots and play with electronics.He started work on a high-tech company after his father asked him to make a robot that would shovel snow for him.Waelbers plans to start sales in early 2017.

For anyone who hates doing yard work，your new best friend may have arrived.A robot can autonomously shovel snow，collect leaves and cut grass.
“We’re trying to help people not spend time on yard work，”said Steven Waelbers，the designer of the robot.“We want people to enjoy their free time with their family.”
The electric robot can run by itself in right directions with the help of two beacons （信号塔）that must be placed in the yard.The robot includes a camera and ultrasound sensor （超声传感器）that Waelbers said would stop quickly when it finds pets and people.
Owners of the robot will need to regulate the values stored in the robot.Then it will confirm the task it’s going to take.Before the robot operates by itself，an owner must manually wheel it around the yard –taking it around any obstacles like trees，bushes or mailboxes.By doing this，the robot is taught how long and wide the lawn is，and won’t accidentally destroy your rose bush or run to the neighborhood.
Once this setup is complete，and the $3，999robot has been trained on where to cut grass，rake leaves and shovel snow，it operates without any supervision.
Waelbers has always loved to build robots and play with electronics.He started work on a high-tech company after his father asked him to make a robot that would shovel snow for him.Waelbers plans to start sales in early 2017.

For anyone who hates doing yard work，your new best friend may have arrived.A robot can autonomously shovel snow，collect leaves and cut grass.
“We’re trying to help people not spend time on yard work，”said Steven Waelbers，the designer of the robot.“We want people to enjoy their free time with their family.”
The electric robot can run by itself in right directions with the help of two beacons （信号塔）that must be placed in the yard.The robot includes a camera and ultrasound sensor （超声传感器）that Waelbers said would stop quickly when it finds pets and people.
Owners of the robot will need to regulate the values stored in the robot.Then it will confirm the task it’s going to take.Before the robot operates by itself，an owner must manually wheel it around the yard –taking it around any obstacles like trees，bushes or mailboxes.By doing this，the robot is taught how long and wide the lawn is，and won’t accidentally destroy your rose bush or run to the neighborhood.
Once this setup is complete，and the $3，999robot has been trained on where to cut grass，rake leaves and shovel snow，it operates without any supervision.
Waelbers has always loved to build robots and play with electronics.He started work on a high-tech company after his father asked him to make a robot that would shovel snow for him.Waelbers plans to start sales in early 2017.

For anyone who hates doing yard work，your new best friend may have arrived.A robot can autonomously shovel snow，collect leaves and cut grass.
“We’re trying to help people not spend time on yard work，”said Steven Waelbers，the designer of the robot.“We want people to enjoy their free time with their family.”
The electric robot can run by itself in right directions with the help of two beacons （信号塔）that must be placed in the yard.The robot includes a camera and ultrasound sensor （超声传感器）that Waelbers said would stop quickly when it finds pets and people.
Owners of the robot will need to regulate the values stored in the robot.Then it will confirm the task it’s going to take.Before the robot operates by itself，an owner must manually wheel it around the yard –taking it around any obstacles like trees，bushes or mailboxes.By doing this，the robot is taught how long and wide the lawn is，and won’t accidentally destroy your rose bush or run to the neighborhood.
Once this setup is complete，and the $3，999robot has been trained on where to cut grass，rake leaves and shovel snow，it operates without any supervision.
Waelbers has always loved to build robots and play with electronics.He started work on a high-tech company after his father asked him to make a robot that would shovel snow for him.Waelbers plans to start sales in early 2017.