Threshold effects in the Teaching Space Allocation Problem with Splitting

Universities aim for good “Space Management” so as to use the teaching space efficiently. Part of this task is to assign rooms and time-slots to teaching activities with limited numbers and capacities of lecture theaters, seminar rooms, etc. It is also common that some teaching activities require splitting into multiple events. For example, lectures can be too large to fit in one room or good teaching practice requires that seminars/tutorials are taught in small groups. Then, space management involves decisions on splitting as well as the assignments to rooms and time-slots. These decisions must be made whilst satisfying the pedagogic requirements of the institution and constraints on space resources. The efficiency of such management can be measured by the “utilisation”: the percentage of available seat-hours actually used. In many institutions, the observed utilisation is unacceptably low, and this provides our underlying motivation: to study the factors that affect teaching space utilisation, with the goal of improving it. We give a brief introduction to our work in this area, and then introduce a specific model for splitting. We present experimental results that show threshold phenomena and associated easy-hard-easy patterns of computational difficulty. We discuss why such behaviour is of importance for space management.

A balanced polymorphism in biomass resource allocation controlled by phosphate in grasses screened through arsenate tolerance

The response of arsenate and non-tolerant Holcus lanatus L. phenotypes, where tolerance is achieved through suppression of high affinity phosphate/arsenate root uptake, was investigated under different growth regimes to investigate why there is a polymorphism in tolerance found in populations growing on uncontaminated soil. Tolerant plants screened from an arsenic uncontaminated population differed, when grown on the soil from the populations origin, from non-tolerants, in their biomass allocation under phosphate fertilization: non-tolerants put more resources into tiller production and down regulated investment in root production under phosphate fertilization while tolerants tillered less effectively and did not alter resource allocation to shoot biomass under phosphate fertilization. The two phenotypes also differed in their shoot mineral status having higher concentrations of copper, cadmium, lead and manganese, but phosphorus status differed little, suggesting tight homeostasis. The polymorphism was also widely present (40%) in other wild grass species suggesting an important ecological role for this gene that can be screened through plant root response to arsenate.

Energy-Aware Rate and Description Allocation Optimized Video Streaming for Mobile D2D Communications

The proliferation problem of video streaming applications and mobile devices has prompted wireless network operators to put more efforts into improving quality of experience (QoE) while saving resources that are needed for high transmission rate and large size of video streaming. To deal with this problem, we propose an energy-aware rate and description allocation optimization method for video streaming in cellular network assisted device-to-device (D2D) communications. In particular, we allocate the optimal bit rate to each layer of video segments and packetize the segments into multiple descriptions with embedded forward error correction (FEC) for realtime streaming without retransmission. Simultaneously, the optimal number of descriptions is allocated to each D2D helper for transmission. The two allocation processes are done according to the access rate of segments, channel state information (CSI) of D2D requester, and remaining energy of helpers, to gain the highest optimization performance. Simulation results demonstrate that our proposed method (named OPT) significantly enhances the performance of video streaming in terms of high QoE and energy saving.