Lingmin Zhang

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A graph G is said to be chromatic-choosable if ch(G)= (G). Ohba has conjectured that every graph G with 2 (G)+ 1 or fewer vertices is chromatic-choosable. It is clear that Ohba’s conjecture is true if and only if it is true for complete multipartite graphs. But for complete multipartite graphs, the graphs for which Ohba’s conjecture has been verified are(More)
By analyzing data yielded from a sample of Chinese adolescents surviving a high-intensity earthquake, this study investigated the underlying dimensionality of DSM-5 PTSD symptoms. The sample included 743 traumatized middle school students (396 females and 332 males) aged 11-17 years (mean=13.6, SD=1.0). Results of confirmatory factor analysis showed that an(More)
Servers and network contribute about 60% to the total cost of data center in cloud computing. How to efficiently place virtual machines so that the cost can be saved as much as possible, while guaranteeing the quality of service plays a critical role in enhancing the competitiveness of service cloud provider. Considering the heterogeneous servers and the(More)
In this paper, we study the issue of minimizing the total energy cost for green cloud data centers with time varying and location varying electricity prices and supply of renewable energy. Given the budget of energy cost, schedule the requests, servers, and power usage of different sources, such that the total cost can be minimized. We formulate the problem(More)
The new curriculum standard gives higher requirements to the teaching ability of middle school mathematics teachers, such as: the ability of teaching students how to learn well, applying new teaching theory and modern information technology, and exploiting and using curriculum resources. For this, middle school mathematics teachers should improve their(More)
A graphG is called chromatic-choosable if its choice number is equal to its chromatic number, namely Ch(G) = χ(G). Ohba has conjectured that every graph G satisfying |V (G)| ≤ 2χ(G)+1 is chromatic-choosable. Since each k-chromatic graph is a subgraph of a complete k-partite graph, we see that Ohba’s conjecture is true if and only if it is true for every(More)