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SDN-based Handover in Future WLAN
Syed Mushhad M. Gilani,Wenqiang Jin 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.12
Presently, the smart devices consumers prefer IEEE 802.11-based wireless local area network (WLAN) to access the Internet due to ease of access, low cost, tremendous throughput, and provision for multimedia applications. However, traditional WLAN suffers from a critical issue regarding handover management because it has not been well-announced in IEEE 802.11 according to future Internet demands. Researchers argue that Software Defined Network (SDN) be future Internet technology revolution that brings significant impact on a wireless network. In this paper, we propose a framework within the SDN paradigm, which enables mobility management, load balancing, and position management applications on top of the centralized controller. The proposed framework implements load targeted handover (LTH) scheme for mobile stations to offers seamless handover and targeted association with underloaded APs. We evaluate LTH approach in a simulation environment then implement in real-time WLAN tested, and results demonstrate that SDN-enabled handover process leads to consistent throughput as compared to a traditional approach.
Hong Zong,Xiaohong Liu,Wenqiang Chen,Bin Zhuge,Jin Sun 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.5
1,3-Propanediol (1,3-PDO) is an important three-carbon compound widely used in new polyester polymer materials. Natural organisms that can produce 1,3- PDO from glycerol were well studied. However, no natural microorganisms found could directly convert glucose to 1,3-PDO due to its insufficient glycerol synthesis pathway. In this study, two essential glycerol synthesis genes, CgGPD gene (encoding glycerol-3-phosphate dehydrogenase from Candida glycerinogenes) and ScGPP2 gene (encoding glycerol-3-phosphatase from Saccharomyces cerevisiae), were expressed in wild-type Klebsiella pneumoniae, a natural 1,3-PDO producers with reduction pathway for 1,3- PDO synthesis from glycerol. The results of fermentation, key enzyme activities, and metabolites analysis confirmed that recombinant K. pneumoniae now possessed a metabolic pathway capable of converting glucose to 1,3-PDO. The strain could produce 1,3-PDO from glucose with a final titer of 17.27 g/L with 40 g/L glucose in the medium, showing a 1.26-fold increase compared with 30 g/L glucose. Also, adding certain concentrations of glycerol could quickly initiate the 1,3-PDO synthetic pathway and promote the accumulation of 1,3-PDO, which could shorten the fermentation cycle. These results have important implications for further studies involving the use of one strain for bioconversion of glucose to 1,3-PDO.
New ZVZCT Bidirectional DC-DC Converter Using Coupled Inductors
Qian, Wei,Zhang, Xi,Li, Zhe,Jin, Wenqiang,Wiedemann, Jochen The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
In this study, a novel zero voltage zero current transition (ZVZCT) bidirectional DC-DC converter is proposed by employing coupled inductors. This converter can turn the main switch on at ZVZCT and it can turn it off with zero voltage switching (ZVS) for both the boost and buck modes. These characteristics are obtained by using a simple auxiliary sub-circuit regardless of the power flow direction. In the boost mode, the auxiliary switch achieves zero current switching (ZCS) turn-on and ZVS turn off. Due to the coupling inductors, this converter can make further efficiency improvements because the resonant energy in the capacitor or inductor can be transferred to the load. The main diode operates with ZVT turn-on and ZCS turn-off in the boost mode. For the buck mode, there is a releasing circuit to conduct the currents generated by the magnetic flux leakage to the output. The auxiliary switch turns on with ZCS and it turns off with ZVT. The main diode also turns on with ZVT and turns off with ZCS. The design method and operation principles of the converter are discussed. A 500 W experimental prototype has been built and verified by experimental results.
New ZVZCT Bidirectional DC-DC Converter Using Coupled Inductors
Wei Qian,Xi Zhang,Zhe Liu,Wenqiang Jin,Jochen Wiedemann 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
In this study, a novel zero voltage zero current transition (ZVZCT) bidirectional DC-DC converter is proposed by employingcoupled inductors. This converter can turn the main switch on at ZVZCT and it can turn it off with zero voltage switching (ZVS)for both the boost and buck modes. These characteristics are obtained by using a simple auxiliary sub-circuit regardless of thepower flow direction. In the boost mode, the auxiliary switch achieves zero current switching (ZCS) turn-on and ZVS turn off. Due to the coupling inductors, this converter can make further efficiency improvements because the resonant energy in thecapacitor or inductor can be transferred to the load. The main diode operates with ZVT turn-on and ZCS turn-off in the boostmode. For the buck mode, there is a releasing circuit to conduct the currents generated by the magnetic flux leakage to the output. The auxiliary switch turns on with ZCS and it turns off with ZVT. The main diode also turns on with ZVT and turns off withZCS. The design method and operation principles of the converter are discussed. A 500 W experimental prototype has been builtand verified by experimental results.