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Enhancing subspace clustering based on dynamic prediction

Frontiers of Computer Science 2019年第4期13卷 802-812页

作者： ratha pech Dong HAO Hong CHENG Tao ZHOU Complex Lab University of Electronic Science and Technology of China Chengdu 611731 China Big Data Research Center University of Electronic Science and Technology of China Chengdu 611731 China Center for Robotics University of Electronic Science and Technology of China Chengdu 611731 China

In high dimensional data, many dimensions are irrelevant to each other and clusters are usually hidden under noise. As an important extension of the traditional clustering, subspace clustering can be utilized to simultaneously cluster the high dimensional data into several subspaces and associate the low-dimensional subspaces with the corresponding points. In subspace clustering, it is a crucial step to construct an affinity matrix with block-diagonal form, in which the blocks correspond to different clusters. The distance-based methods and the representation-based methods are two major types of approaches for building an informative affinity matrix. In general, it is the difference between the density inside and outside the blocks that determines the efficiency and accuracy of the clustering. In this work, we introduce a well-known approach in statistic physics method, namely link prediction, to enhance subspace clustering by reinforcing the affinity matrix. More importantly, we introduce the idea to combine complex network theory with machine learning. By revealing the hidden links inside each block, we maximize the density of each block along the diagonal, while restrain the remaining non-blocks in the affinity matrix as sparse as possible. Our method has been shown to have a remarkably improved clustering accuracy comparing with the existing methods on well-known datasets.

关键词： subspace clustering link prediction blockdiagonal matrix low-rank representation sparse representation.

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Characterization of Sandstone Reservoir at Bokor Formation, Kampot Province, Kampong Som Basin, Onshore Cambodia

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International Journal of Geosciences 2023年第8期14卷 792-811页

作者： Vechheka Oeur Chanmoly Or Chandoeun Eng Sopheap pech Lytheng Thorng Sreymean Sio ratha Heng Research and Innovation Center Institute of Technology of Cambodia Phnom Penh Cambodia Faculty of Geo-Resources and Geotechnical Engineering Institute of Technology of Cambodia Phnom Penh Cambodia

Kampong Som Basin is a Paleozoic-Mesozoic sedimentary basin located in southern Cambodia. While the sandstone of the Bokor Formation is expected to be the reservoir for hydrocarbon accumulation. Hence, this study aims to define the properties, quality, and factors that control reservoir rock quality. Sandstones of the Bokor Formation are sampled and analyzed using a helium porosimeter, nitrogen permeameter, polarized light microscope, and scanning electron microscope (SEM) to check the porosity, permeability, minerals, pore geometry, and clay minerals that influence the reservoir quality. According to the result of petrography analysis described by thin section, the sandstone samples from Bokor formation are classified as quartz arenite that composes mainly of quartz, rock fragment, mica-flake, and sericite with connected and unconnected pores of 50 μm to 500 μm with interparticle pore type. Sandstones in this formation have porosity values ranging from 6.55% to 13.19%, and permeability values ranging from 10 mD to 60 mD. The statistics of porosity and permeability of sandstone reservoirs indicate low porosity and permeability that are suggested to be fair reservoir rock for hydrocarbon accumulation. SEM results indicate that there are three types of authigenic clay minerals involving such as kaolinite, illite, and chlorite. In addition, the pore geometry, quartz overgrowth, dissolution of quartz and felspar grain filling in pore space, compaction, replacement diagenesis processes, and cementation presence of clay minerals are the main controlling factors of the sandstone reservoir from the Bokor Formation. Furthermore, this area exhibits sedimentary structures such as planar cross-bedding, cross-bedding, parallel lamination, normal grading, massive, wavy, and reverse graded bedding, which indicates these lithofacies may be deposited in shallow marine environments.

关键词： Sandstone Reservoir rock Bokor Formation Kampong Som Basin Depositional Environment Hydrocarbon Reservoir

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Depositional Environment of Sediments in Tonle Sap Sedimentary Basin, Western Part of Cambodia: Insights from Field and Geochemical Studies

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Open Journal of Geology 2023年第7期13卷 651-666页

作者： Sopheap pech Chandoeun Eng Chanmoly Or Afikah Binti Rahim ratha Heng Chitra Buth Sreymean Sio Research and Innovation Center Institute of Technology of Cambodia Phnom Penh Cambodia Faculty of Geo-Resources and Geotechnical Engineering Institute of Technology of Cambodia Phnom Penh Cambodia Faculty of Engineering Universiti Teknologi Malaysia Johor Malaysia Faculty of Engineering Chulalongkorn University Bangkok Thailand

Tonle Sap sedimentary basin was considered a favorable geological condition for hydrocarbon accumulation in the onshore Cambodia. Two exposure outcrops in Battambang province, called Somlout and Takream, were selected to represent sediments in this basin. The sedimentology and geochemistry studies provide insights into the depositional environment of sediments using field investigation, lithological, sedimentological, paleontological, and geochemical analysis. The redox condition, water column, and depositional setting were analyzed by plotting the ratio of V vs. Cr, Uauthigenic vs. V/Cr, Sr vs. Ba, Ca vs. (Fe + Ca), and Fe2O3/TiO2 vs. Al2O3/(Al2O3 + Fe2O3) diagram. Moreover, these diagrams can be used to predict depositional conditions as well. Based on the results, Somlout and Takream comprise calcareous shale and limestone facies. The geochemical analysis showed that Somlout calcareous shale samples were deposited in the dysoxic freshwater of the lake setting during the regression, while Somlout limestones and Takream were deposited in high salinity seawater, oxic condition of shallow-marine water. In addition, Somlout limestones consist of fragmental fusulinid foraminifera, bivalve shelve, and bryozoan, which suggest a barrier environment. Meanwhile, Teakream consists of fine-grained calcareous shale, and lime-mudstone, which are presented to form in the quiet marine setting of the lagoon environment. Therefore, the Tonle Sap basin sediments were deposited in the Somlout area’s barrier and lake environment, and the lagoon environment for Takream.

关键词： Depositional Environment Sedimentary Basin Geochemistry Paleontology Tonle Sap

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