Northeastern University (China)

About: Northeastern University (China) is a education organization based out in Shenyang, China. It is known for research contribution in the topics: Microstructure & Control theory. The organization has 36087 authors who have published 36125 publications receiving 426807 citations. The organization is also known as: Dōngběi Dàxué & Northeastern University (东北大学).

Mining frequent itemsets over uncertain databases

Abstract: In recent years, due to the wide applications of uncertain data, mining frequent itemsets over uncertain databases has attracted much attention. In uncertain databases, the support of an itemset is a random variable instead of a fixed occurrence counting of this itemset. Thus, unlike the corresponding problem in deterministic databases where the frequent itemset has a unique definition, the frequent itemset under uncertain environments has two different definitions so far. The first definition, referred as the expected support-based frequent itemset, employs the expectation of the support of an itemset to measure whether this itemset is frequent. The second definition, referred as the probabilistic frequent itemset, uses the probability of the support of an itemset to measure its frequency. Thus, existing work on mining frequent itemsets over uncertain databases is divided into two different groups and no study is conducted to comprehensively compare the two different definitions. In addition, since no uniform experimental platform exists, current solutions for the same definition even generate inconsistent results. In this paper, we firstly aim to clarify the relationship between the two different definitions. Through extensive experiments, we verify that the two definitions have a tight connection and can be unified together when the size of data is large enough. Secondly, we provide baseline implementations of eight existing representative algorithms and test their performances with uniform measures fairly. Finally, according to the fair tests over many different benchmark data sets, we clarify several existing inconsistent conclusions and discuss some new findings.

An Aluminum-Sulfur Battery with a Fast Kinetic Response.

Abstract: The electrochemical performance of the aluminum-sulfur (Al-S) battery has very poor reversibility and a low charge/discharge current density owing to slow kinetic processes determined by an inevitable dissociation reaction from Al2 Cl7- to free Al3+ . Al2 Cl6 Br- was used instead of Al2 Cl7- as the dissociation reaction reagent. A 15-fold faster reaction rate of Al2 Cl6 Br- dissociation than that of Al2 Cl7- was confirmed by density function theory calculations and the Arrhenius equation. This accelerated dissociation reaction was experimentally verified by the increase of exchange current density during Al electro-deposition. Using Al2 Cl6 Br- instead of Al2 Cl7- , a kinetically accelerated Al-S battery has a sulfur utilization of more than 80 %, with at least four times the sulfur content and five times the current density than that of previous work.

Electrodeposition of vanadium oxide–polyaniline composite nanowire electrodes for high energy density supercapacitors

Abstract: To meet the increasing demand for high energy density supercapacitors, it is crucial to develop positive and negative electrodes with comparable energy density. Previous studies have primarily focused on the development of positive electrodes, while negative electrodes are relatively less explored. Here we report an electro-codeposition method to synthesize a high performance negative electrode composed of a vanadium oxide (V2O5) and polyaniline (PANI) composite. Scanning electron microscopy revealed that the composite film is composed of one-dimensional polymer chains. Energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) confirmed successful incorporation of V2O5 into PANI chains. Significantly, the V2O5–PANI composite nanowires exhibited a wide potential window of 1.6 V (between −0.9 and 0.7 V vs. SCE) and a maximum specific capacitance of 443 F g−1 (664.5 mF cm−2). The flexible symmetric supercapacitor assembled with this composite film yielded a maximum energy density of 69.2 W h kg−1 at a power density of 720 W kg−1, and a maximum power density of 7200 W kg−1 at an energy density of 33.0 W h kg−1. These values are substantially higher than those of other pure V2O5 or PANI based supercapacitors. Moreover, the assembled symmetric supercapacitor device showed an excellent stability with 92% capacitance retention after 5000 cycles. The capability of synthesizing high performance composite electrodes using the electro-codeposition method could open up new opportunities for high energy density supercapacitors.