In this paper, a model of two-wave mixing in the photorefractive crystal, which takes account of the difference in spatial frequency in a beam, has been built to study the image enhancement effect in coherent optical amplification. Based on the theoretical analysis of the model, the gain distribution for each pixel in the signal beam has been obtained. It shows that the unevenness of the gain i...

MOOSE Crossing is a text-based virtual reality environment (or “MUD”) designed to be a constructionist learning environment for children ages 8 to 12. We performed a portfolio-style assessment of children’s programming accomplishments in this environment. Analysis of the data reveals uneven levels of achievement—some children accomplish a great deal but the majority learn little. We believe thi...

The air-gap nucleation time, the stress evolution and the solid shell growth pattern are examined for different mold topographies to illustrate the potential control of aluminum cast surface morphologies during the early stages of solidification using proper design of mold topographies. The interaction between heat transfer and deformation during the early stages of solidification is considered...

Virtual worlds are three-dimensional, computer-generated worlds where team collaboration is facilitated through the use of shared virtual space. In this research, we are interested in studying the effect of task complexity on team collaboration. We use a puzzle as the collaboration task and manipulate task complexity using the number of puzzle pieces. We hypothesize that task complexity will in...

In this paper, a new type of total spray tray (TST) with gas–liquid countercurrent contact is proposed to solve the problem slight operation flexibility and poor sloshing resistance in towers under offshore conditions. Its hydrodynamic performance indicators, such as pressure drop, weeping, entrainment, liquid level unevenness, were experimentally studied rolling motion. A tower an inner diamet...

Horizontal wellswith multi-cluster fracturing technology is an effective approach to exploit unconventional hydrocarbon reservoirs. The on-site diagnosis results indicate that fractures always tend propagate unevenly due stressinterference, therefore it very essential study the effect of parameters on fracture propagation unevenness. In this paper, model (UFM, Unconventional Fracturing Model) u...

benefits in 1953 ___. lion, private carriers were responsible for 62 percent, State funds for 25 percent, and self-insurers for 13 percent. Total State fund disbursements, including payments to Federal Government employees, again increased at a slightly faster rate than private carrier payments-5.6 percent and 4.4 percent, respectively. The unevenness in the rate of increase from State to State...

Climate changes may affect ecosystems destabilising relationships among species. We investigate the spatial rock-paper-scissors models with a regional unevenness that reduces selection capacity of organisms one Our results show regionally weak species predominates in local ecosystem, while spiral patterns appear far from region, where individuals every play game same strength. Because controls ...

Fungal diseases represent a widely spread natural phenomenon affecting many of wild and domesticated plants. In nature, all plant species forms communities mixed character, the spatial pattern dominant is usually irregular spotted. Some are impregnable to certain infection, which provides kind barrier infection within community. Under agricultural environment, when single may occupy huge area, ...