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Research on Process Modeling of Information Dissemination Based on Social Network
Guohua Zhang,Feng Bao,Zhijun Liu 보안공학연구지원센터 2016 International Journal of Multimedia and Ubiquitous Vol.11 No.7
According to the retweeting mechanism based on user relations, we introduce the contacted state of an agent, and build a model of information propagation process in social networks. In the model, agents have two absorbing states, that is, the infected and refractory state. Experimental prove that small spreading rete can make information diffuse widely, and the degree based density of infected agents increases with the degree monotonously. The influence between information occurs only when different information originates in the same local neighborhood.
Designing an Early Warning Indicator System for Logistics Companies' Reputation Risk
Guohua Zhang,Jiali Yuan 인하대학교 정석물류통상연구원 2009 인하대학교 정석물류통상연구원 학술대회 Vol.2009 No.10
The early warning system of the reputation risk of logistic companies is the core of the early warning management of this risk. It is the foundation for the structure of a general evaluation model in the reputation risk of logistics companies. The model consists of seven categories of secondary indicators, they are product reliability risk, business reputation risk; logistics service credibility risk, financial credibility risk, legal credibility risk, social reputation risk and credit risk, and twenty eight third degree indicators.
Parallel Collaborative Filtering Recommendation Algorithm based on Cloud Computing
Guohua Zhang,Feng Bao,Sheng Bai 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.7
The paper Proposed Item parallel collaborative filtering recommendation algorithm (IP-CF). Through designing efficient parallel algorithm, compute-extensive procedures are distributed to different processing nodes in Hadoop platform. Taking advantage of parallel computing, we accelerate the response of recommendation. The experimental results show that our proposed algorithm IP-CF is more efficient and scalable than current parallel algorithms.
Zhang, Xi,Xu, Jianping,Wu, Jiahui,Bao, Bocheng,Zhou, Guohua,Zhang, Kaitun The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.
Xi Zhang,Jianping Xu,Jiahui Wu,Bocheng Bao,Guohua Zhou,Kaitun Zhang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5
The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.
Uncertainty analysis of containment dose rate for core damage assessment in nuclear power plants
Guohua Wu,Jiejuan Tong,Yan Gao,Liguo Zhang,Yunfei Zhao 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.5
One of the most widely used methods to estimate core damage during a nuclear power plant accident iscontainment radiation measurement. The evolution of severe accidents is extremely complex, leading touncertainty in the containment dose rate (CDR). Therefore, it is difficult to accurately determine coredamage. This study proposes to conduct uncertainty analysis of CDR for core damage assessment. First,based on source term estimation, the Monte Carlo (MC) and point-kernel integration methods were usedto estimate the probability density function of the CDR under different extents of core damage in accidentscenarios with late containment failure. Second, the results were verified by comparing the resultsof both methods. The point-kernel integration method results were more dispersed than the MC results,and the MC method was used for both quantitative and qualitative analyses. Quantitative analysisindicated a linear relationship, rather than the expected proportional relationship, between the CDR andcore damage fraction. The CDR distribution obeyed a logarithmic normal distribution in accidents with asmall break in containment, but not in accidents with a large break in containment. A possible applicationof our analysis is a real-time core damage estimation program based on the CDR
Guohua Zheng,Xianqian Niu,Jinbiao Zhang,Hanwen Wu,Xiuxiang Lin,Dongming Pan 한국원예학회 2015 원예과학기술지 Vol.33 No.3
In this experiment, five commercial cultivars and one wild species of loquat were used to investigate frost tolerance and enzymatic activities in leaves and young fruits under cold stress at -3℃. The frost injury, malondialdehyde (MDA) content, and oxygen-scavenging enzyme activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were studied. This results showed that the wild species ‘Wild Oak-leaf’ loquat was the most frost tolerant among accessions tested, followed by the cultivar ‘Golden Block’. Other cultivars, ‘Wu Gong Bai’, ‘Taicheng 4’, ‘Xiangzhong 11’ and ‘Zaozhong 6’, were relatively weak in frost tolerance. The enzymatic activities of SOD, POD and CAT increased initially and then decreased as the exposure time increased. However, the enzymatic peak occurred later in the frost-tolerant accession than in the frost-sensitive accession. The correlation coefficients of MDA contents between leaves and immature fruits were from 0.93 to 0.99 in the five commercial loquat cultivars. For the ‘Wild Oak-leaf’ loquat, the correlation coefficients of MDA and POD were 0.98 and 0.95, respectively, but the coefficients for SOD, CAT and APX were relatively low. In general, there were good correlations between loquat leaves and immature fruits in MDA content and enzyme activities. These results indicate that analysis of these physiological and biochemical activities in loquat leaves could potentially be used to predict the cold tolerance in loquat at immature fruit stage and to accelerate breeding programs for cold tolerance in loquat.
rGO/VNTs as cathodes for high performance sodium ion batteries with good cycling performance
Guohua Gao,Mingze Ji,Kun Zhang,Guangming Wu 대한금속·재료학회 2022 ELECTRONIC MATERIALS LETTERS Vol.18 No.1
Using the ex-situ composite method, we have prepared grapheme coating vanadium oxide nanotubes (VNT) by using vanadium oxide nanotubes, cationic surfactant cetyltrimethylammonium bromide (CTAB) and graphene oxide (GO) aqueous solution. The surface of the vanadium oxide nanotube was modified by CTAB, so that vanadium oxide nanotubes were combined with graphene oxide via electrostatic interaction. The introduction of graphene provides an effective protective layer for vanadium oxide nanotubes, alleviates the volume change caused by sodium ion insertion and extraction during charge and discharge process, and enhances the stability of vanadium oxide nanotube structure. The electrochemical test show that the capacity retention of VNTs after 50 cycles was only 18%, while the capacity retention rate of VNTs/rGO was as high as 74%. In addition, we made a detailed analysis of the morphology, structure and formation mechanism of the materials.