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Digital Dead-Time Control for an Integrated Tri-Mode Buck-Boost DC-DC Converter
J.S. Yu,G. Jin,S.L. Cheng,W.T. Ng 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Traditional fixed dead-time driving strategy can lead to unwanted body-diode conduction or momentary cross-conduction. Since the optimum dead-time varies with the load current, it is important to continuously adjust the dead-time on a cycle by cycle basis. The turning on and off of the switching node also require different dead-times. This paper introduces a digital continuous dead-time correction circuit that can adjust the optimum timing for both the rising and falling edges of the output switching waveform for an integrated non-inverting tri-mode DC-DC converter. The converter is designed to operate with a Li-ion battery as the input power supply (2.7 V to 4.2 V) and to provide an output voltage ranging from 1 V to 5 V. An improvement in peak power conversion efficiency of 3% is observed when the output current varies from 0 to 0.5 A with a switching frequency of 1.5 MHz.
Bioprocessing for elimination antibiotics and hormones from swine wastewater
Cheng, D.L.,Ngo, H.H.,Guo, W.S.,Liu, Y.W.,Zhou, J.L.,Chang, S.W.,Nguyen, D.D.,Bui, X.T.,Zhang, X.B. Elsevier 2018 Science of the Total Environment Vol.621 No.-
<P><B>Abstract</B></P> <P>Antibiotics and hormones in swine wastewater have become a critical concern worldwide due to the severe threats to human health and the eco-environment. Removal of most detectable antibiotics and hormones, such as sulfonamides (SAs), SMs, tetracyclines (TCs), macrolides, and estrogenic hormones from swine wastewater utilizing various biological processes were summarized and compared. In biological processes, biosorption and biodegradation are the two major removal mechanisms for antibiotics and hormones. The residuals in treated effluents and sludge of conventional activated sludge and anaerobic digestion processes can still pose risks to the surrounding environment, and the anaerobic processes' removal efficiencies were inferior to those of aerobic processes. In contrast, membrane bioreactors (MBRs), constructed wetlands (CWs) and modified processes performed better because of their higher biodegradation of toxicants. Process modification on activated sludge, anaerobic digestion and conventional MBRs could also enhance the performance (e.g. removing up to 98% SMs, 88.9% TCs, and 99.6% hormones from wastewater). The hybrid process combining MBRs with biological or physical technology also led to better removal efficiency. As such, modified conventional biological processes, advanced biological technologies and MBR hybrid systems are considered as a promising technology for removing toxicants from swine wastewater.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biological antibiotics and hormones treatment process for swine wastewater was reviewed. </LI> <LI> Mechanisms of antibiotics/hormones removal can be biosorption and biodegradation. </LI> <LI> Conventional AS and AD are ineffective for antibiotics & hormones removal. </LI> <LI> MBRs/hybrid MBRs and constructed wetlands can improve toxicants removal. </LI> <LI> Modified conventional bioreactors are also efficient in antibiotics and hormones removal. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>