A Model for Coopetition Evolution of Software Industrial Virtual Cluster

Liu Kewen,Gao Changyuan 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.3

The application of complex network theory can clearly reveal the coopetition activities between inter-members in software industrial virtual cluster. The research result shows that neither simplex cooperation nor competition,but it is a kind of dynamic equilibrium of coopetition. The empirical is analyzed by using the example of cloud computing. In the process of coopetition evolution, the distribution functions of node strength are from random to power law and eventually to random.

Coopetition Co-existence Model for Software Industrial Virtual Cluster Based on Business Ecosystems

Liu Kewen,Gao Changyuan 보안공학연구지원센터 2016 International Journal of u- and e- Service, Scienc Vol.9 No.6

Coopetition is an important driving force for the formation and sustainable development of Software Industrial Virtual Clusters. But the process of participating in the global coopetition of software enterprises is very complicated. This paper analyzed the characteristic of coopetition in Software Industrial Virtual Clusters by using the theory of business ecosystems, coopetition co-existence model of Software Industrial Virtual Cluster was established, introducing competition coefficient and cooperation coefficient on the basis of Tilman’s research. The results of simulation show that the condition of coopetition co-existence is the competitive ability has a nonlinear minus correlation with cooperation ability. The empirical study also found that the initial share is an important factor affecting the competitive advantage.

The Framework of Social Networks Big Data Processing Based on Cloud Computing

Liu Kewen,Gao Changyuan 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.10

With the rise of cloud computing, internet of things, social networks, the type and scale of data in human society has increased at an unprecedented rate, making data from being a simple object to be process to being a basic resource. Fully mining the value of data resources that was hidden in SNS such Weibo Microblog, Wechat has become a common subject concerned by industrial circle, academic area and government departments. Although the distributed storage and analysis of cloud computing platform have been widely used in big data process of social networks, it has not been able to fully solve the problems of big data storage and process in social networks. In this paper, it proposed the big data process framework of social networks based on cloud computing. By adopting the mixing cloud model and coordinating the data storage framework and data computing framework, and regarding social networks features such as real-time, sharing, mobility, individuation, and interactivity, this big data process framework can be adopted to process large-scale massive amount of data, to research the unified management and sharing strategy of massive data, to propose data process strategy and the service application of big data such as Microblog and Wechat, and to discuss several urgent key problems in processing social networks big data.

Identification of Dominant Microbial Community and Diversity in Continuously Cropped Pepper Fields

Hui Wang,Li Liu,Shuyi Yu,Tianshu Guan,Baihong Li,Qi Wang,Changyuan Liu 한국원예학회 2021 원예과학기술지 Vol.39 No.4

Pepper blight is the most significant soil-borne disease affecting the continuous cropping of peppers. To identify the effect of Phytophthora capsici infection on microbial flora, we isolated and counted the microorganisms collected from the rhizosphere soil of P. capsici-affected farms that continuously cropped pepper for 3, 6, and 9 years in Liaoning Province, China. The colony and cell morphology, physiological and biochemical characteristics, and 16S rDNA sequence of bacteria and actinomycetes were documented. In addition, colony and microscopic morphology of fungi and the rDNA-ITS sequence were analysed for classification. We observed that healthy and diseased peppers had the largest number of bacteria in the rhizosphere followed by actinomycetes and fungi. After infection, the number of bacteria and actinomycetes decreased with a corresponding increase in the number of fungi, leading to a reduction in the ratio of bacteria/fungi to actinomycetes/fungi. We identified 15 dominant bacterial strains, of which Bacillus represented the most abundant genus consisting of 7 strains followed by Flavobacterium and Staphylococcus. Furthermore, 15 of the 17 actinomycetes strains belonged to the genus Streptomyces. Among the six fungal strains, we found P. infestans, Fusarium, and Penicillium consisting of two strains each. This study elucidated the impact of pathogenic P. capsici on the composition of soil microbes over time and characterized several cultivatable dominant bacterial groups, which can provide a basis for practical intervention strategies to improve soil conditions for continuous cropping.

Comparison of Dynamic Characteristics between Virtual Synchronous Machines Adopting Different Active Power Droop Controls

Chang Yuan,Chang Liu,Xueyin Zhang,Tianyang Zhao,Xiangning Xiao,Niang Tang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

In modern power systems, high penetration of distributed generators (DGs) results in high stress on system stability. Apart from the intermittent nature of DGs, most DGs do not contribute inertia or damping to systems. As a result, a new control method named virtual synchronous machine (VSM) was proposed, which brought new characteristics to inverters such as synchronous machines (SMs). In addition, different active power droop controls for VSMs are being proposed in literatures. However, they are quite different in terms of their dynamic characteristics despite of the similar control laws. In this paper, mathematical models of a VSM adopting different active power droop controls are built and analyzed. The dynamic performance of the VSM output active power and virtual rotor angular frequency are presented for different models. The influences of the damping factor and droop coefficient on the VSM dynamic behaviors are also investigated in detail. Finally, the theoretical analysis is verified by simulations and experimental results.

Transient Characteristics and Physical Constraints of Grid-Tied Virtual Synchronous Machines

Chang Yuan,Chang Liu,Dan Yang,Ruibing Zhou,Niang Tang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.4

In modern power systems, distributed generators (DGs) result in high stress on system frequency stability. Apart from the intermittent nature of DGs, most DGs do not contribute inertia or damping to systems. As a result, a new control method referred to as a virtual synchronous machine (VSM) has been proposed, which brought new characteristics to inverters such as synchronous machines (SM). DGs employing an energy storage system (ESS) provide inertia and damping through VSM control. Meanwhile, energy storage presents some physical constraints in the VSM implementation level. In this paper, a VSM mathematical model is built and analyzed. The dynamic responses of the output active power are presented when a step change in the frequency occurs. The influences of the inertia constant, damping factor and operating point on the ESS volume margins are investigated. In addition, physical constraints are proposed based on these analyses. The proposed physical constraints are simulated using PSCAD/EMTDC software and tested through RTDS experiment. Both simulation and RTDS test results verify the analysis.

Small-Signal Modeling and Control of Three-Phase Bridge Boost Rectifiers under Non-Sinusoidal Conditions

Chang, Yuan,Jinjun, Liu,Xiaoyu, Wang,Zhaoan, Wang The Korean Institute of Power Electronics 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.5

This paper proposes a systematic approach to the modeling of the small-signal characteristics of three-phase bridge boost rectifiers under non-sinusoidal conditions. The main obstacle to the conventional synchronous d-q frame modeling approach is that it is unable to identify a steady-state under non-sinusoidal conditions. However, for most applications under non-sinusoidal conditions, the current loops of boost rectifiers are designed to have a bandwidth that is much higher than typical harmonics frequencies in order to achieve good current control for these harmonic components. Therefore a quasi-static method is applied to the proposed modeling approach. The converter small-signal characteristics developed from conventional synchronous frame modeling under different operating points are investigated and a worst case point is then located for the current loop design. Both qualitative and quantitative analyses are presented. It is observed that operating points influence the converter low frequency characteristics but hardly affect the dominant poles. The relationship between power stage parameters, system poles and zeroes is also presented which offers good support for the system design. Both the simulation and experimental results verified the analysis and proposed modeling approach. Finally, the practical case of a parallel active power filter is studied to present the modeling approach and the resultant regulator design procedure. The system performance further verifies the whole analysis.