MR-CLOPE: A Map Reduce based transactional clustering algorithm for DNS query log analysis

DNS(domain name system) query log analysis has been a popular research topic in recent years. CLOPE, the represented transactional clustering algorithm, could be readily used for DNS query log mining. However, the algorithm is inefficient when processing large scale data. The MR-CLOPE algorithm is proposed, which is an extension and improvement on CLOPE based on Map Reduce. Different from the previous parallel clustering method, a two-stage Map Reduce implementation framework is proposed. Each of the stage is implemented by one kind Map Reduce task. In the first stage, the DNS query logs are divided into multiple splits and the CLOPE algorithm is executed on each split. The second stage usually tends to iterate many times to merge the small clusters into bigger satisfactory ones. In these two stages, a novel partition process is designed to randomly spread out original sub clusters, which will be moved and merged in the map phrase of the second phase according to the defined merge criteria. In such way, the advantage of the original CLOPE algorithm is kept and its disadvantages are dealt with in the proposed framework to achieve more excellent clustering performance. The experiment results show that MR-CLOPE is not only faster but also has better clustering quality on DNS query logs compared with CLOPE.

Local records of long-term dynamics of bamboo gregarious flowering in northern Laos and regional synchronicity of Dendrocalamus membranaceus in two flowering sites

Bamboos are widely distributed in mainland Southeast Asia and have abundant biomass. They are characterized by prolonged vegetative growth and semelparity. Where bamboos are dominant, their synchronous flowering and death has a major impact on forest vegetation. Although the small-scale dynamics of this process have become clearer in recent years, the history, geographical scale and synchronicity of bamboo flowering over broad areas remains unknown. This study focused on the flowering history of six bamboo species, Bambusa tulda, Cephalostachyum virgatum, Dendrocalamus hamiltonii, Dendrocalamus membranaceus, Indosasa sinica and Oxytenanthera parvifolia, over 40 years across a broad area of northern Laos. We also examined the synchronicity of flowering in D. membranaceus. We visited 49 villages in northern Laos and surveyed knowledgeable inhabitants about bamboo flowering history. The timing, scale and synchronicity of gregarious flowering varied among species. D. hamiltonii and D. membranaceus showed higher flowering synchronicity than other species. All the species except I. sinica had both sporadic and gregarious flowering traits, and showed conspicuous variability in their flowering scale. The flowering bamboo population at two gregarious flowering sites for D. membranaceus was surveyed. While thisspecies had the highest synchronicity in this study, its synchronicity was lower than other species in previous studies worldwide. We found that the gregarious flowering of bamboos in northern Laos over the last 40 years showed lower synchronicity than bamboo flowering reported in other areas of the world. The historical dynamics and scale of bamboo flowering must be further clarified to understand the vegetation composition of this area.

Depositional environment of terrestrial petroleum source rocks and geochemical indicators in the Songliao Basin

To determine geochemical indicators for depositional environment favored by terrestrial petroleum source rocks, we selected 40 source rock samples from the Late Cretaceous Qingshankou Formation （Kzqn） and the first member of Nenjiang Formation （K2n1） in the Songliao Basin to qualify saturate fraction and aromatic fraction using GC-HRT （gas chromatography high resolution time-of-flight mass spectrometry） and quantify important biomarkers using GC-MS. The results reveal that source rocks from the 1st member of Qingshankou Formation （K2qn1） are characterized by not only high contents of terpanes, regular steranes and 4-methylsteranes but also high contents of dinosteranes, C31 steranes and aryl isoprenoids. Presence of specific biomarkers like elementary sulfur and lanostanes indicates a depositional environment of lagoon characterized by water stratification and high salinity. In the 2nd-3rd members of Qingshankou Formation （K2qn2＋3）, source rocks contain lower contents of biomarkers, indicating a depositional environment of shallow fresh-water lake delta. Source rocks in the K2n1 contain high contents of terpanes, regular steranes and 4-methylsteranes but lower contents of dinosteranes, C31 steranes and aryl isoprenoids, indicating a depositional environment of fresh-brackish open lake characterized by low salinity and poor water stratification, where organic matter is seriously altered by bacteria. Overall analysis shows that primary geochemical indicators for terrestrial petroleum source rocks are as follows： 1） C30 hopanes 〉 1500 ppm; 2） gammacerane 〉190 ppm; 3） C27 steranes 〉200 ppm; 4） 4-methylsteranes 〉 100 ppm; 5） aryl isoprenoids 〉 3 ppm; 6） dehydroxyl-vitamin E 〉 10 ppm.