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Shunt-diode rectifier: a new scheme for efficient piezoelectric energy harvesting
Brenes, Alexis,Lefeuvre, Elie,Badel, Adrien,Seok, Seonho,Yoo, Chan-Sei Institute of Physics Publishing 2019 Smart materials & structures Vol.28 No.1
<P>This paper highlights the interest of shunt-diode rectifiers to optimize the performances of piezoelectric vibration energy harvesters based on linear load adaptation. It provides, for the first time, a full analytical study of the input power and frequency bandwidth of such a system. We show that this architecture is well-suited for piezoelectric energy harvesting. In the presented approach, a so-called shunt diode is connected across the electrodes of the piezoelectric transducer, which makes the piezoelectric voltage unidirectional instead of alternating. Thus, DC–DC converters usually used for power optimization can be directly connected to the transducer. We show that weakly-coupled linear inertial piezoelectric energy harvesters generate higher power when connected to a shunt-diode rectifier than to a bridge rectifier. Moreover, the frequency bandwidth is enlarged by the use of the single-diode shunt rectifier, especially for strongly-coupled piezoelectric generators. The proposed architecture is also interesting for low piezoelectric voltages, at which voltage drops across the diodes used for AC–DC conversion critically degrade the power efficiency. Experimental results validate the presented analytical study and highlight the higher efficiency of the shunt-diode rectifier circuit. Compared to a standard bridge rectifier architecture, we demonstrate an increase of +43% output power on a weakly-coupled generator and an increase of +5% bandwidth on a strongly-coupled generator.</P>
Gao, Yihuai,Gao, He,Chan, Eli,Tan, Wenbo,Lan, Jin,Koh, Hwee-Ling,Chen, Guoliang,Zhou, Shufeng The Korean Society of Food Science and Nutrition 2004 Preventive Nutrition and Food Science Vol.9 No.3
A recent randomized and double-blind placebo-controlled clinical study bas indicated that Ganoderma lucidum polysaccharides (GLP) decrease blood glucose in patients with type II diabetes. The aim of this study was to investigate the effect of the GLP extract in alloxan-induced diabetic rats. Oral administration of GLP at 0.25, 0.5 and 1.0 g/kg for 4 weeks resulted in a reduction of blood glucose levels by 12.5, 18.7 and 33.7% respectively, while glibenclamide treatment brought the hyperglycemic value down to normal. The hyperglycemic effect was supported by a significant decrease in glycosylated haemoglobin and increased plasma insulin levels (p<0.01) in a dose- and time-dependent manner. This study showed that GLP has similar hypoglycemic effects as glibenclamide in alloxan-induced diabetic rats.
Yihuai Gao,He Gao,Eli Chan,Wenbo Tan,Jin Lan,Hwee-Ling Koh,Guoliang Chen,Shufeng Zhou 한국식품영양과학회 2004 Preventive Nutrition and Food Science Vol.9 No.3
A recent randomized and double-blind placebo-controlled clinical study has indicated that Ganoderma lucidum polysaccharides (GLP) decrease blood glucose in patients with type II diabetes. The aim of this study was to investigate the effect of the GLP extract in alloxan-induced diabetic rats. Oral administration of GLP at 0.25, 0.5 and 1.0 g/kg for 4 weeks resulted in a reduction of blood glucose levels by 12.5, 18.7 and 33.7% respectively, while glibenclamide treatment brought the hyperglycemic value down to normal. The hypoglycemic effect was supported by a significant decrease in glycosylated haemoglobin and increased plasma insulin levels (p<0.01) in a dose- and time-dependent manner. This study showed that GLP has similar hypoglycemic effects as glibenclamide in alloxan-induced diabetic rats.
Unipolar synchronized electric charge extraction for piezoelectric energy harvesting
Brenes, Alexis,Lefeuvre, Elie,Badel, Adrien,Seok, Seonho,Yoo, Chan-Sei Institute of Physics Publishing 2018 Smart materials & structures Vol.27 No.7
<P>This paper highlights the interest of a shunt rectifier to improve the efficiency of the synchronized electric charge extraction (SECE) circuit formerly developed for piezoelectric energy harvesters. Compared to the classical SECE circuit, which requires a full-bridge rectifier, the proposed architecture is especially interesting for low-amplitude vibrations generating a low piezoelectric voltage, typically lower than 2 V RMS. We provide a full analytical study validated by experimental measurements to illustrate the high performance of the so-called unipolar SECE (USECE) as well as the impact of the resonator characteristics on the overall performance of the harvester. We also propose a model including the main causes of power dissipation, which is validated experimentally, showing that the power efficiency of the circuit is much less dependent on the vibration frequency and magnitude than classical SECE. The proposed architecture combines the high input power of SECE with the high power efficiency resulting from unipolar operation, reaching more than 75% power efficiency in situations where classical SECE is limited to an efficiency lower than 35%. Our experimental results show an increase of +200% output power obtained with USECE compared to classical SECE, which is due to the combination of a higher input power and a higher power efficiency of the proposed circuit.</P>
Ganoderma lucidum Polysaccharide Fractions Accelerate Healing of Acetic Acid-Induced Ulcers in Rats
Shufeng Zhou,Wenbo Tang,He Gao,Eli Chan,Jin Lan,Yihuai Gao 한국식품영양과학회 2004 Journal of medicinal food Vol.7 No.4
The polysaccharide (PS) fractions from several medicinal herbs have been reported to have antiulcer effects against experimental ulcer in the rat. The watersoluble PS fractions from G. lucidum (Reishi mushroom) have been shown to inhibit indomethacin-induced gastric mucosal lesions in rats. This study aimed to investigate the effect of the PS fraction from G. lucidum on the healing of gastric ulcer induced by acetic acid in the rat and to elucidate the underlying mechanisms involved. The abdomen of rats was incised and the stomach treated with 10 M acetic acid (100 l) for 1 min, and then treated with G. lucidum PS (0.1, 0.5 or 1.0 g/kg) intragastrically, once a day for 14 consecutive days. The results indicated that the oral administration of G. lucidum PS at 0.5 and 1.0 g/kg for 2 weeks caused a significant acceleration of the ulcer healing by 40.1% and 55.9%, respectively. In the mechanistic studies, additional rats were treated with 10 M acetic acid to induce acute ulcers, and then treated with G. lucidum PS (1.0 g/kg) for 3, 7, 10 or 14 days. Exposure of the rat stomach to acetic acid led to decreased mucus and increased prostaglandin levels. Treatment of G. lucidum PS at 1.0 g/kg significantly (P < 0.05) suppressed or restored the decreased gastric mucus levels and increased gastric prostaglandin concentrations compared to the control group. These results indicates that G. lucidum PS is an active component with healing efficacy on acetic acid-induced ulcer in the rat, which may represent a useful herbal preparation for the prevention and treatment of peptic ulcers.
Shufeng Zhou,Yihuai Gao,Wenbo Tang,Xihu Dai,He Gao,Guoliang Chen,Jinxian Ye,Eli Chan,Hwee Lling Koh,Xiaotian Li 한국식품영양과학회 2005 Journal of medicinal food Vol.8 No.2
Preclinical studies have established that the polysaccharide fractions of Ganoderma lucidumhave potential an-titumor activity. Recent clinical studies have demonstrated that G. lucidumpolysaccharides enhance host immune functions[e.g., enhanced natural killer (NK) cell activity] in patients with advanced solid tumors, although an objective response wasnot observed. This open-label study aimed to evaluate the effects of water-soluble G. lucidumpolysaccharides (Ganopoly??,Encore International Corp., Auckland, New Zealand) on immune functions in patients with advanced lung cancer. Thirty-sixpatients were enrolled and treated with 5.4 g/day Ganopoly for 12 weeks. In the 30 cancer patients who completed the trial,treatment with Ganopoly did not significantly alter the mean mitogenic reactivity to phytohemagglutinin, mean counts of CD3,CD4, CD8, and CD56, mean plasma concentrations of interleukin (IL)-2, IL-6, and interferon (IFN)-., or NK activity in thepatients, but the results were significantly variable. However, some cancer patients demonstrated markedly modulated im-mune functions. The changes in IL-1 were correlated with those for IL-6, IFN-., CD3, CD8, and NK activity (P. .05), andIL-2 changes were correlated with those for IL-6, CD8, and NK activity. The results suggest that subgroups of cancer patientsmight be responsive to Ganopoly in combination with chemotherapy/radiotherapy. Further studies are needed to explore theefficacy and safety of Ganopoly used alone or in combination with chemotherapy/radiotherapy in lung cancer patients.