Based on Rock Failure Process Analysis model RFPA2D, the evolutionary proc- esses of failure process of rock mass with multiple natural joints were simulated. Numeri- cal simulations show that anisotropy of compressiv...Based on Rock Failure Process Analysis model RFPA2D, the evolutionary proc- esses of failure process of rock mass with multiple natural joints were simulated. Numeri- cal simulations show that anisotropy of compressive strength of jointed rock mass varies with the number of natural joints and inclination of natural joints. As the number of natural joints in rock mass increases, the anisotropy becomes less and less. It is justifiable to treat approximately rock mass containing six or more natural joints instead of four or more joints that was described in literature of Hoek and Brown as isotropy.展开更多
The round-tailed homed lizard Phrynosoma modestum is cryptically colored and resembles a small stone when it draws legs close to its body and elevates its back. We investigated effectiveness of camouflage in P. modest...The round-tailed homed lizard Phrynosoma modestum is cryptically colored and resembles a small stone when it draws legs close to its body and elevates its back. We investigated effectiveness of camouflage in P. modestum and its dependence on stones by placing a lizard in one of two microhabitats （uniform sand or sand with surface rocks approximately the same size as lizards）. An observer who knew which microhabitat contained the lizard was asked to locate the lizard visually. Latency to detec- tion was longer and probability of no detection within 60 s was higher for lizards on rock background than on bare sand. In arenas where lizards could choose to occupy rock or bare sand, much higher proportions selected rocky backgrounds throughout the day; at night all lizards slept among stones. A unique posture gives P modestum a rounded appearance similar to many natural stones. Lizards occasionally adopted the posture, but none did so in response to a nearby experimenter. Stimuli that elicit the posture are unknown. That P. modestum is better camouflaged among rocks than on bare sand and prefers to occupy rocky areas suggests that special resemblance to rocks （masquerade） enhances camouflage attributable to coloration and immobility.展开更多
Yujia Stone Village,situated in Jingxing County in North China’s Hebei Province,dates back more than 500 years.The village,surrounded by mountains is like a natural city in which nearly 100 quadrangles are made out o...Yujia Stone Village,situated in Jingxing County in North China’s Hebei Province,dates back more than 500 years.The village,surrounded by mountains is like a natural city in which nearly 100 quadrangles are made out of stone houses and cave dwellings.When one visits the village,he/she is sure to be impressed by the stone buildings,the stone utensils and the village’s simple and pristine customs. Moreover,one is also—inclined to gasp at the beauty—especially the depth of the Taihang Mountains—of the village,which is far removed from the hustle and bustle of urban areas.No wonder so many people refer to the village as "heaven of peace."展开更多
基金Supported by the National 973 Planning Project(2007CB209404)the Doctoral Research Foundation of Dalian University(0302221)
文摘Based on Rock Failure Process Analysis model RFPA2D, the evolutionary proc- esses of failure process of rock mass with multiple natural joints were simulated. Numeri- cal simulations show that anisotropy of compressive strength of jointed rock mass varies with the number of natural joints and inclination of natural joints. As the number of natural joints in rock mass increases, the anisotropy becomes less and less. It is justifiable to treat approximately rock mass containing six or more natural joints instead of four or more joints that was described in literature of Hoek and Brown as isotropy.
文摘The round-tailed homed lizard Phrynosoma modestum is cryptically colored and resembles a small stone when it draws legs close to its body and elevates its back. We investigated effectiveness of camouflage in P. modestum and its dependence on stones by placing a lizard in one of two microhabitats （uniform sand or sand with surface rocks approximately the same size as lizards）. An observer who knew which microhabitat contained the lizard was asked to locate the lizard visually. Latency to detec- tion was longer and probability of no detection within 60 s was higher for lizards on rock background than on bare sand. In arenas where lizards could choose to occupy rock or bare sand, much higher proportions selected rocky backgrounds throughout the day; at night all lizards slept among stones. A unique posture gives P modestum a rounded appearance similar to many natural stones. Lizards occasionally adopted the posture, but none did so in response to a nearby experimenter. Stimuli that elicit the posture are unknown. That P. modestum is better camouflaged among rocks than on bare sand and prefers to occupy rocky areas suggests that special resemblance to rocks （masquerade） enhances camouflage attributable to coloration and immobility.
文摘Yujia Stone Village,situated in Jingxing County in North China’s Hebei Province,dates back more than 500 years.The village,surrounded by mountains is like a natural city in which nearly 100 quadrangles are made out of stone houses and cave dwellings.When one visits the village,he/she is sure to be impressed by the stone buildings,the stone utensils and the village’s simple and pristine customs. Moreover,one is also—inclined to gasp at the beauty—especially the depth of the Taihang Mountains—of the village,which is far removed from the hustle and bustle of urban areas.No wonder so many people refer to the village as "heaven of peace."
