Crystallization on a sphere
Abstract We present a parallel simulated annealing algorithm for crystallization of N -body systems. The implementation uses systolic simulated annealing with additional parallel cost function evaluation. We have a hybrid topology which consists of a systolic ring and attached to each ring processor a tree of processors. Our research topic is crystallization of particles on a spherical surface. Some results of the crystallization experiments are presented.
Distributed scheduling for disconnected cooperation
Ability to cooperate on common tasks in a distributed setting is key to solving a broad range of computation problems ranging from distributed search such as SETI to distributed simulation and multi-agent collaboration. In such settings there exists a trade-off between computation and communication: both resources must be managed to decrease redundant computation and to ensure efficient computational progress. This paper deals with scheduling issues for distributed collaboration. Specifically, we examine the extreme situation where initially collaboration must occur without communication. That is, we consider the extent to which efficient collaboration is possible if all resources are directed to computation at the expense of communication. The results summarized here precisely characterize the ability of distributed agents to collaborate on a known collection of independent tasks by means of local scheduling decisions that require no communication and that achieve low redundancy in task executions. Such scheduling solutions exhibit an interesting connection between the distributed collaboration problem and the design theory. The lower bounds presented here along with the randomized and deterministic schedule constructions show the limitations on such low-redundancy cooperation and show that schedules with near-optimal redundancy can be efficiently constructed by processors working in isolation.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.