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This paper presents an unsupervised clustering random-forest-based metric for affinity estimation in large and high-dimensional data. The criterion used for node splitting during forest construction can handle rank-deficiency when measuring cluster compactness. The binary forest-based metric is extended to continuous metrics by exploiting both the common traversal path and the smallest shared parent node.The proposed forest-based metric efficiently estimates affinity by passing down data pairs in the forest using a limited number of decision trees. A pseudo-leaf-splitting (PLS) algorithm is introduced to account for spatial relationships, which regularizes affinity measures and overcomes inconsistent leaf assign-ments. The random-forest-based metric with PLS facilitates the establishment of consistent and point-wise correspondences. The proposed method has been applied to automatic phrase recognition using color and depth videos and point-wise correspondence. Extensive experiments demonstrate the effectiveness of the proposed method in affinity estimation in a comparison with the state-of-the-art.

The recent issued emission regulations have more stringent standards for the transient emissions of natural gas engines. When equipped with cooled exhaust gas recirculation (EGR) and three way catalyst (TWC), natural gas engines operating at stoichiometric conditions are capable of achieving extremely low transient emissions. In this paper, the transient emission characteristics of a heavy-duty natural gas engine at stoichiometric operation with EGR and TWC are experimentally studied based on the world harmonized transient cycle (WHTC). The results show that both the raw carbon monoxide (CO) and total hydrocarbon (THC) emissions are higher in the hot start test while the raw NOx emissions are higher in the cold start test. When measurements are conducted after the TWC, all these emissions are higher in the cold start test. Among all the sub-cycles of WHTC, the urban sub-cycle plays the most important role for all three emissions in both cold start and hot start conditions except the after three way catalyst (ATWC) CO emissions in the cold start test, where the motorway sub-cycle takes up the highest percentage. In summary, CO, nitrogen oxide (NOx) as well as non-methane hydrocarbon (NMHC) emissions can meet the requirements of Euro VI emission standards, whereas CH 4 emissions are higher than the corresponding standard, suggesting that improvements in the performance of the catalyst are essential.

Adding hydrogen to natural gas is a promising way to improve the ignition stability and reduce the greenhouse gas emissions of pilot-ignition direct-injection natural gas engines. Most of the previous studies concerning hydrogen-enriched natural gas engines are focused on spark-ignition engines. The limited investigations on the addition of hydrogen in direct-injection natural gas engines are conducted by experimental method. Therefore, some detailed information on the in-cylinder combustion and emission formation process are left unknown. In this work, numerical simulations have been performed for the combustion process of a pilot-ignition direct-injection natural gas engine based on an integrated mechanism which is capable of describing the chemical kinetics involving diesel, natural gas, and hydrogen. Three-dimensional (3D) computational fluid dynamics simulations were conducted at different hydrogen blend ratios to explore the effects of hydrogen addition on the whole combustion process and the mole f...

The large PV medium-voltage (MV) DC power collection system is more efficient than the traditional AC collection system, which provides an alternative for future PV applications. As one of the core components of the PV MVDC power collection system, key techniques of DC transformer are presented here in detail, including the technical requirements, and fault operation analysis in the DC collection system. When part of the PV DC module in the low-voltage (LV) side of DC transformer fails and bypassed, the DC collection system continues working normally with only part of power lost. When the MV side of DC transformer is shorted, all the PV modules exist and the collection system splits without ride-through techniques. The fault operation principle of DC transformer in PV MVDC power collection system is verified by simulations.

In this study, we investigate the extent to which patent citations to papers can serve as early signs for predicting delayed recognized knowledge in science using a comparative study with a control group, i.e., instant recognition papers. We identify the two opposite groups of papers by the Bcp measure, a parameter-free index for identifying papers which were recognized with delay. We provide a macro (Science/Nature papers dataset) and micro (a case chosen from the dataset) evidence on paper-patent citation linkages as early signs for predicting delayed recognized knowledge in science. It appears that papers with delayed recognition show a stronger and longer technical impact than instant recognition papers. We provide indication that in the more recent years papers with delayed recognition are awakened more often and earlier by a patent rather than by a scientific paper (also called "prince"). We also found that patent citations seem to play an important role to avoid instant recognition papers to level off or to become a so called "flash in the pan", i.e., instant recognition. It also appears that the sleeping beauties may firstly encounter negative citations and then patent citations and finally get widely recognized. In contrast to the two focused fields (biology and chemistry) for instant recognition papers, delayed recognition papers are rather evenly distributed in biology, chemistry, psychology, geology, materials science, and physics. We discovered several pairs of "science sleeping"-"technology [...]. We propose in further research to discover the potential ahead of time and transformative research by using citation delay analysis, patent & NPL analysis, and citation context analysis., 21 pages, 8 figures, and 4 tables; previous version was presented at the ISSI 2019 in Rome, Italy; current version has been accepted for publication in Journal of Informetrics

The digital gap of e-commerce adoption among countries is widening. To better understand this phenomenon, this article reviews the latest research on the key factors of firm's e-commerce adoption and proposes a comprehensive framework as part of addressing the current literature gap. Based on this, managerial implications and future research directions are also discussed.