China University of Petroleum

About: China University of Petroleum is a education organization based out in Beijing, China. It is known for research contribution in the topics: Catalysis & Oil shale. The organization has 39802 authors who have published 39151 publications receiving 483760 citations. The organization is also known as: Zhōngguó Shíyóu Dàxué & China University of Petroleum (Beijing).

Hydrothermal conversion of carbohydrate biomass to lactic acid

Abstract: We investigated the hydrothermal conversion of the carbohydrates including glucose, cellulose, and starch to lactic acid using NaOH and Ca(OH)2 as alkaline catalysts. Both catalysts significantly promoted the lactic acid formation. The highest yield of lactic acid from glucose was 27% with 2.5 M NaOH and 20% with 0.32 M Ca(OH)2 at 300°C for 60 s. The lactic acid yields from cellulose and starch were comparable with the yield from glucose with 0.32 M Ca(OH)2 at 300°C, but the reaction time in the case of cellulose was 90 s. The mechanism of lactic acid formation from glucose was discussed by identifying the intermediate products. Lactic acid may be formed via the formation of aldoses of two to four carbons including aldose of three carbons, which are all formed by reverse aldol condensation and double bond rule of hexose. This implies that carbon–carbon cleavage occurs at not only C3C4 but also at C2C3. © 2010 American Institute of Chemical Engineers AIChE J, 2010

Tuning the self-assembly of short peptides via sequence variations

Abstract: Peptide self-assembly is of direct relevance to protein science and bionanotechnology, but the underlying mechanism is still poorly understood. Here, we demonstrate the distinct roles of the noncovalent interactions and their impact on nanostructural templating using carefully designed hexapeptides, I2K2I2, I4K2, and KI4K. These simple variations in sequence led to drastic changes in final self-assembled structures, beta-sheet hydrogen bonding was found to favor the formation of one-dimensional nanostructures, such as nano-fibrils from I4K2 and nanotubes from KI4K, but the lack of evident beta-sheet hydrogen bonding in the case of I2(K2)I(2) led to no nanostructure formed. The lateral stacking and twisting of the beta-sheets were well-linked to the hydrophobic and electrostatic interactions between amino acid side chains and their interplay. For I4K2, the electrostatic repulsion acted to reduce the hydrophobic attraction between beta-sheets, leading to their limited lateral stacking and more twisting, and final fibrillar structures; in contrast, the repulsive force had little influence in the case of KI4K, resulting in wide ribbons that eventually developed into nanotubes. The fibrillar and tubular features were demonstrated by a combination of cryogenic transmission electron microscopy (cryo-TEM), negative-stain transmission electron microscopy (TEM), and small-angle neutron scattering (SANS). SANS also provided structural information at shorter scale lengths. All atom molecular dynamics (MD) simulations were used to suggest possible molecular arrangements within the beta-sheets at the very early stage of self-assembly.

Remaining Useful Life Estimation of Structure Systems Under the Influence of Multiple Causes: Subsea Pipelines as a Case Study

Abstract: In dynamic complex environments, the degradation of structure systems is generally caused not by a single factor but by multiple ones, and the process is subject to a high level of uncertainty. This article contributes a hybrid physics-model-based and data-driven remaining useful life (RUL) estimation methodology of structure systems considering the influence of multiple causes by using dynamic Bayesian networks (DBNs). The structure model and parameter model of DBNs for the degradation process caused by a single factor are established on the basis of theoretical or empirical physical models, thereby solving the problem of insufficient data. An RUL estimation model is subsequently established by integrating these degradation process models. The RUL value is obtained from the time difference between the detection point and predicted failure point, which is determined using the failure threshold of performance. The sensor data and expert knowledge can be input into the estimation model to update the RUL value whenever necessary. The subsea pipelines in offshore oil and gas subsea production systems are adopted to demonstrate the proposed methodology. The degradation processes with fatigue, corrosion, sand erosion, and internal waves are modeled using DBNs, and the RUL is estimated using a DBN-based RUL methodology.

Enhancing Capacitance Performance of Ti 3 C 2 T x MXene as Electrode Materials of Supercapacitor: From Controlled Preparation to Composite Structure Construction

Abstract: Ti3C2Tx, a novel two-dimensional layer material, is widely used as electrode materials of supercapacitor due to its good metal conductivity, redox reaction active surface, and so on. However, there are many challenges to be addressed which impede Ti3C2Tx obtaining the ideal specific capacitance, such as restacking, re-crushing, and oxidation of titanium. Recently, many advances have been proposed to enhance capacitance performance of Ti3C2Tx. In this review, recent strategies for improving specific capacitance are summarized and compared, for example, film formation, surface modification, and composite method. Furthermore, in order to comprehend the mechanism of those efforts, this review analyzes the energy storage performance in different electrolytes and influencing factors. This review is expected to predict redouble research direction of Ti3C2Tx materials in supercapacitors.