With 15 million visitors including heads of state due to visit the World Exposition, host Japan will try to ease safety concerns through a display in its own right - security robots.
The Expo, whose exhibits range from a frozen mammoth dug up in Siberia to humanoid robots, opens to the public on Friday with guests to include Japanese Emperor Akihito and Prime Minister Junichiro Koizumi, French President Jacques Chirac, Australian Prime Minister John Howard and Central American leaders.
The six-month Expo, which traces its history to the 1851 Great Exhibition in London, aims to show the cutting edge in technology and innovation with 121 countries setting up displays in a forest park in central Aichi prefecture.
As many as 3,000 police will join some 1,000 private guards at the venue - along with eight security robots who will guide visitors by day and patrol by night.
Designers noted that the robots, while smaller in number, are unlikely to succumb to the fatigue that could afflict the human contingent.
Visitors will be required to go through metal detectors and baggage inspections and be barred from bringing cans, bottles or food. More than 200 security cameras are placed at key points surrounded by infra-red sensors.
'This is the first World Expo in which measures against terrorist attacks are top priority,' said Toshio Nakamura, secretary-general of the Japan Association for the 2005 World Exposition.
Special police squads to handle bombs and chemical weapons will be on stand-by with gas masks and explosive disposal equipment.
'After the Iraq war, we decided to put emphasis on measures against terrorism,' said Yuichi Yokoyama, vice chief of the exposition security office of the Aichi police department.
'We especially beefed up security at pavilions of countries involved in the war such as the United States, Britain, Japan,' Yokoyama told AFP.
For the robotic contingent, organisers make no secret that an ulterior motive is to show off Japanese technology.
'It's a great chance to display the potential for the use of robots for the purpose of security,' said Daisaku Sudo, an official of Japanese robot maker Tmsuk Co. Ltd.
Ligurio, a prototype security robot produced by the company, can move at a maximum speed of seven kilometers (4.3 miles) per hour and recognise a stranger 50 meters (164 feet) away even at night, using microwave sensors.
The 60 million yen (573,000 dollar) robot is equipped with a voice warning system and two folded arms that can grab explosives or lethal chemical containers and remove them to safe places.
In a demonstration, the 150-centimeter (59-inch) robot with a barrel-shaped body and two headlights like eyes removed a fake explosive, saying: 'A dangerous object was found. It will be removed.'
'A robot can be fixed or reproduced when it's broken on duty, but human beings cannot have replacement,' Sudo said.
'We want a lot of visitors to see and touch our robots and realise how useful robots are,' he said, adding that the company hopes to market the robot in about two years.
Guard Robo i, another security robot produced by Sohgo Security Service Co. Ltd., a Japanese firm, can follow strangers and shoot paint bullets at them.
The company said the image of a robot on guard could become increasingly common, as Japan is one of the world's most ageing societies with a potential labour shortage looming.
'Security robots are very realistic, especially in Japan, where it will be more and more difficult to find guards amid the low birthrate,' Takao Ariki, chief of Sohgo Security's robotic technology team.
The concerns of the Expo will be not only human misdeeds but the force of nature, as Japan endures about 20 percent of the world's powerful earthquakes.
'We have stocked enough foods and water to take care of tens of thousands of visitors for at least one full day in case a big earthquake occurs here,' said Yokoyama, the police official.
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