Carbon dioxide reforming of methane over MgO promoted Ni/CNT catalyst

Dehua Zhang,Guangcheng Wei,Yiru Wang,Jing Wang,Ping Ning,Qiulin Zhang,Mingzhi Wang,Tengfei Zhang,Kaixian Long 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.10

Carbon dioxide reforming of methane to syngas was investigated over a series of MgO promoted Ni/CNT catalysts. MgO played a critical role in improving the catalytic performance of Ni/CNT. The results showed that the addition of MgO strengthened the interaction of Ni and interior surface of CNT. Highly dispersed nickel particles with small size (less than 4.5nm) were also observed in MgO modified CNT. Otherwise, the NiO nanoparticles were facilely reduced over the catalyst prepared with a narrow size of CNT, as shown in H2-TPR. The reaction tests demonstrated that the Ni-based catalyst with an addition of MgO and narrow size of CNT exhibited better catalytic activity. Furthermore, the lifetime of Ni-based catalyst was prolonged effectively after adding MgO, attributed to the stabilization and dispersion of Ni particles and the effective restraint on the gasification of CNT.

On the complete convergence for arrays of rowwise extended negatively dependent random variables

Dehua Qiu,Pingyan Chen,Rita Giuliano Antonini,Andrei Volodin 대한수학회 2013 대한수학회지 Vol.50 No.2

A general result for the complete convergence of arrays of rowwise extended negatively dependent random variables is derived. As its applications eight corollaries for complete convergence of weighted sums for arrays of rowwise extended negatively dependent random variables are given, which extend the corresponding known results for independent case.

Commercial Demonstration of biorefinery of lipids-Coproduction of Biodiesel and 1,3-propanediol

Dehua LIU,Xuebing ZHAO,Hongjuan LIU,Keke CHENG 한국생물공학회 2015 한국생물공학회 학술대회 Vol.2015 No.4

An Efficient Parallel Top-k Similarity Join for Massive Multidimensional Data Using Spark

Dehua Chen,Changgan Shen,Jieying Feng,Jiajin Le 보안공학연구지원센터 2015 International Journal of Database Theory and Appli Vol.8 No.3

Top-k similarity join has been used in a wide range of applications that require calculating the most top-k similar pairs of data records in a given database. However, the time performance will be a challenging problem, as an increasing trend of applications that need to process massive data. Obviously, finding the top-k pairs in such vast amounts of data with traditional methods is awkward. In this paper, we propose the RDD-based algorithm to perform the top-k similarity join for massive multidimensional data over a large cluster built with commodity machines using Spark. The RDD- based algorithm consists of four steps, which loads a set of multidimensional records stored in HDFS and finally output an ordered list of top-k closest pairs into HDFS. Firstly, we develop an efficient distance function based on LSH(Locality Sensitive Hashing) to improve the efficiency in pairwise similarity comparison. Secondly, to minimize the amount of data during the RDD running- time, we split conceptually all pairs of LSH signatures into partitions. Moreover, we exploit a serial computation strategy to calculate all top-k closest pairs in parallel. Finally, all the local top-k pairs sorted by their Hamming distances will contribute to the global top-k pairs. In this paper, the performance evaluation between Spark and Hadoop confirms the effectiveness and scalability of our RDD-based algorithm.

Optically tunable Seebeck effect from intramolecular proton-transfer materials in organic vertical thin-film thermoelectric device

Hu, Dehua,Liu, Qing,Tisdale, Jeremy,Nam, Haerim,Park, Soo Young,Wang, Hsin,Urbas, Augustine,Hu, Bin Elsevier 2015 ORGANIC ELECTRONICS Vol.26 No.-

<P><B>Abstract</B></P> <P>This paper reports Seebeck effects from optically-induced intramolecular proton-transfer HPI-Cbz molecules based on vertical electrode/organic film/electrode thin-film devices. We observed large Seebeck coefficients of 428μV/K and 390μV/K from HPI-Cbz based thin-film devices at 60°C when proton-transfer was induced by the photoexcitation of a 325nm laser with an intensity of 12mW/cm<SUP>2</SUP> and 6mW/cm<SUP>2</SUP> respectively. Under dark condition without proton transfer occurring, the Seebeck coefficient was measured to be 342μV/K at 60°C. The Seebeck coefficient enhancement by the induced intramolecular charge transfer can be attributed to the enhanced polarization difference between high- and low-temperature surface due to the stronger electron–phonon coupling followed with the proton-transfer in HPI-Cbz under photoexcitation, and the strength of electron–phonon coupling is proportional to the photoexcitation intensity. The enhanced temperature-dependent electrical polarization between the high and low-temperature surfaces acts as an additional driving force to diffuse the majority charge carriers for the development of a large Seebeck effect. Therefore, using intramolecular proton-transfer presents an effective approach of enhancing Seebeck effect in organic materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Photoinduced proton-transfer states lead to enhancement on Seebeck coefficients. </LI> <LI> Photoinduced proton-transfer states lead to enhancement on electrical conductivity. </LI> <LI> Temperature-dependent polarization acts as a new driving force for Seebeck effect. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

ON THE COMPLETE CONVERGENCE FOR ARRAYS OF ROWWISE EXTENDED NEGATIVELY DEPENDENT RANDOM VARIABLES

Qiu, Dehua,Chen, Pingyan,Antonini, Rita Giuliano,Volodin, Andrei Korean Mathematical Society 2013 대한수학회지 Vol.50 No.2

A general result for the complete convergence of arrays of rowwise extended negatively dependent random variables is derived. As its applications eight corollaries for complete convergence of weighted sums for arrays of rowwise extended negatively dependent random variables are given, which extend the corresponding known results for independent case.

STUDIES ON SYNTHESIS OF METHYL GLYCOLATE AND METHYL METHOXY ACETATE FROM THE COUPLING OF FORMALDEHYDE AND METHYL FORMATE

He, Dehua,Huang, Weiguo,Liu, Jinyao,Zhou, Mingxing,Zhu, Qiming 한국화학공학회 1998 Korean Journal of Chemical Engineering Vol.15 No.5

Catalytic performance of various acids in the coupling reaction of formaldehyde and methyl formate to produce methyl glycolate and methyl methoxy acetate has been studied. The influence of reaction conditions, such as catalyst amount, reaction temperature, reaction time, and molar ratio of formaldehyde to methyl formate, has also been investigated. The results showed that the acid strength had great influence on the reaction, namely, stronger acds had higher activities. It was also found that the reaction temperature and time had significant effect on the reaction, and the preferable conditions were quite different as different acids were used.

일대일로 이니셔티브와 중국 해외직접투자 결정요인 분석

최영준,DEHUA MENG 경희대학교(국제캠퍼스) 국제지역연구원 2020 아태연구 Vol.27 No.3

This study analyzed one-belt-one-road(OBOR) initiative and the determinants and the pattern of China’s foreign direct investment. The OBOR Initiative is China’s core political and diplomatic policy that affects foreign direct investment. This study analyzed China’s foreign direct investments in 130 countries from 2008 to 2017 using the GLS model based on the gravity model. The results of the study showed that GDP and the distance which determines the transaction cost, and whether or not a free trade agreement are significant. And the resoureces of destination countries are significant where its R&D is not significant. The OBOR is shown as an important factor that determine the pattern of FDI where it does not affect its FDI quantatively. The pattern of FDI of China in the target countries of OBOR is different from that of non-target countries. In other words, FDI of China is concentrated in countries with abundant energy resources in the OBOR route target countries, and in the countries rich in labor in the non-target countries. 본 연구는 중국의 일대일로 이니셔티브와 해외직접투자의 결정요인과 패턴을 분석하였다. 일대일로 이니셔티브는 중국의 핵심적 정치외교 정책으로서 해외직접투자에 영향을 미친다. 이에 본 연구는 중력모형을 활용하여 2008년부터 2017년까지 130개국에 대한 중국의 해외직접투자 자료를 GLS 모형으로 분석하였다. 본 연구 결과 중국의 해외직접투자에 영향을 미치는 요인은 중력모형에서 나타나는 것과 같이 경제규모와 거래비용을 결정하는 거리와 자유무역협정 체결 여부에 의해 영향을 받는 것으로 나타났다. 다음으로 투자 대상국의 경제적 요소인 부존자원은 유의미한 영향을 미치고 있으나 연구개발비는 유의미하지 않았다. 중국의 일대일로 이니셔티브는 중국의 해외직접투자에 유의미한 영향을 미치지는 않았다. 하지만 중국의 해외직접투자는 일대일로 대상국과 비대상국에 대한 투자패턴이 다르게 나타났다. 일대일로 이니셔티브 대상국에 대한 중국의 투자는 에너지 및 자원을 확보하기 위한 목적이 있는 것으로 나타났다. 하지만 비대상국에 대해서는 낮은 임금의 노동력을 활용하여 생산비용을 낮추기 위한 목적으로 투자하는 것으로 나타났다.

Experimental investigation on the contribution of gas molecular diffusion to gas mass flux in micro-nano pores

Jing Sun,Dehua Liu,Xiang Zhu,Wenjun Huang,Liang Cheng 한국자원공학회 2020 Geosystem engineering Vol.23 No.1

The mass transfer from the matrix to the fracture face is driven by both concentration and pressure differences. In this work, high-temperature high-pressure (HPHT) systems for diffusion experiments with only concentration differences were used to determine the diffusion coefficient, and flow experiments with only pressure differences were also conducted; and the magnitude of gas molecular diffusion and its contribution to production were analyzed in this study. The results show as follows: (1) Gas flow from the matrix to the fracture system is driven by the combined effect of gas molecular diffusion and seepage. The pore structure characteristics of the reservoir and the contribution of the diffusion to the yield can vary greatly. (2) In tight reservoirs with an average permeability of 0.3067 mD, the contribution of gas molecular diffusion to the total gas mass flux is only 0.08%, while in shale reservoirs, the average permeability is 0.0015 mD; the contribution of diffusion to the total gas mass flux could be as large as 1%. (3) The contribution of molecular diffusion to gas production is closely related to the pore sizes of the porous medium. The smaller the pore sizes are, the greater the contribution of molecular diffusion to gas production.

Research on profile inversion controlling methods of multi-slug polymer alternative injection

Ailing Zheng,Dehua Liu,Yanlin Shao 한국자원공학회 2020 Geosystem engineering Vol.23 No.2

The development practice of polymer flooding shows that the injection profile easily inverses during the process of single slug polymer flooding. The low effective or ineffective circulation of abundant injecting water in high permeability layer, low producing degree of low permeability layer and large polymer volume have influenced the sweep efficiency and oil recovery of polymer flooding. In view of these questions, the alternative injection method of various viscosity polymer slugs is studied. This paper explains the theory of enhanced oil recovery of multi-slug polymer alternative injection. The experiment results show that the alternative injection of high and low viscosity polymer slugs has a better effect than single slug polymer flooding. The mobility differences between high-low permeability layers can be effectively reduced. For a multi-layer heterogeneous reservoir, there is an optimal alternative cycle. Reasonable slug size can not only inhibit dominant channel forming in high permeability layer but also can effectively produce low permeability layer and control profile inversion to a certain extent. This provides a technical support for studying the controlling methods of profile inversion.