This paper proposes a novel double series resonant dc-dc converter with uniform voltage stress on a
transformer. It consists of a half-bridge inverter with two power switches (IGBTs), two series resonant
tank, two high-voltage transformers and a symmetrical voltage multiplier circuit. A symmetrical voltage
multiplier circuit is connected at the secondary side of the high voltage transformer to generate desired
high voltage dc output. Due to use of voltage multiplier circuit, the proposed converter requires smaller
turns ratio of the high voltage transformer, leading to reduction in size and volume of the transformer.
The proposed converter operates in discontinuous current mode by varying the switching frequency of
the converter. In a discontinuous current mode operation, all the power switches and output diodes of the
rectifier circuit turn-on and turn-off under zero current switching conditions. Therefore, it has features
of low switching losses and possibility of light-load operation. Besides, it costs less and is smaller in
size compared with conventional double series resonant dc-dc converter. It also has a simple operating
principle and suitable for high voltage and high power applications. Experimental results confirm the
proposed converter performs better than the others.
This paper proposes a half-bridge LLC resonant converter with two resonant tanks for plug-in electric
vehicle (PEV) battery charging. Each resonant tank is connected with one of the centre-tapped primary
windings of the power transformer. Both resonant tanks are fed alternately by a half cycle of the switching
pulse in one period. The converter is designed to operate below resonance zero-voltage switching (ZVS)
region to reduce switching losses and to achieve output DC voltage range 250V-420V with 400V input
DC voltage for depleted PEV battery. MATLAB Simulink is used to simulate the circuit with 1.5 kW
maximum power and the simulation results show that the converter can meet the constant-current,
constant-voltage (CC-CV) charging requirements of the depleted PEV battery.
Introduction: Spray dry is a single step of drying method to transform the fluid materials to dry particles. Common practice for producing the solid form is by using the freeze dry technique. However, the existing freeze dry process was associated with longer drying process, high maintenance and costly. Alternatively, researchers used spray drying during extraction process, yet, an elevated drying temperature applied may incur some effects on the quality and quantity of the extract. Therefore, the present study was aimed to investigate the thermal effect of spray drying process on the quality of spray dried Ficus deltoidea (F.deltoidea). Methods: The thermal effects of spray drying were identified at three different inlet air temperatures (160 oC, 191 oC and 220 oC) which are minimum, optimum and maximum of inlet air temperature, respectively. The Box-Behnken Design through response surface methodology was utilized to identify the optimum operating conditions at these temperatures. The quality of F. deltoidea in terms of yield, moisture content, marker compound (vitexin), total saponins, total protein and total polysaccharides were studied. Results: From the study, total saponins and polysaccharides exhibited better retentions during the spray drying process. Meanwhile, vitexin and total protein was found decreasing by 30% and 50% respectively, during the spray drying process. Conclusion: High operating of air inlet temperatures in spray drying process contribute to higher process yield, produce non-sticky particles with lower moisture contents compared to drying process at 160 oC.
Herbal plants are traditionally utilized to treat various illnesses. They contain phytochemicals that can be extracted using conventional methods such as maceration, soxhlet, and boiling, as well as non-conventional methods including ultrasonic, microwave, and others. Carica papaya leaves have been used for the treatment of dengue, fungal, and bacterial infections as well as an ingredient in anti-aging products. Phytochemicals analysis detected the presence of kaempferol, myricetin, carpaine, pseudocarpaine, dehydrocarpaine I and II, ferulic acid, caffeic acid, chlorogenic acid, β-carotene, lycopene, and anthraquinones glycoside. Conventional preparation by boiling and simple maceration is practical, simple, and safe; however, only polar phytochemicals are extracted. The present study aims to investigate the effects of three different non-conventional extraction techniques (ultrasonic-assisted extraction, reflux, and agitation) on C. papaya phytochemical constituents, the antioxidant capacity, and wound-healing activities. Among the three techniques, the reflux technique produced the highest extraction yield (17.86%) with the presence of saponins, flavonoids, coumarins, alkaloids, and phenolic metabolites. The reflux technique also produced the highest 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging with an IC50 value of 0.236 mg/mL followed by ultrasonic-assisted extraction (UAE) (IC50: 0.377 mg/mL) and agitation (IC50: 0.404 mg/mL). At tested concentrations (3.125 µg/mL to 500 µg/mL), all extracts do not exhibit a cytotoxicity effect on the human skin fibroblast, HSF1184. Interestingly, reflux and UAE were active fibroblast proliferators that support 85% (12.5 µg/mL) and 41% (6.25 µg/mL) better cell growth, respectively. Additionally, during the early 24 h of the scratch assay, the migration rate at 12.5 µg/mL was faster for all extracts with 51.8% (reflux), 49.3% (agitation), and 42.5% (UAE) as compared to control (21.87%). At 48 h, proliferated cells covered 78.7% of the scratch area for reflux extract, 63.1% for UAE, 61% for agitation, and 42.6% for control. Additionally, the collagen synthesis was enhanced for 31.6% and 65% after 24 and 48 h of treatment for reflux. An HPLC-MS/MS-QTOF (quadruple time-of-flight) analysis of reflux identified nine phytochemicals, including carpaine, kaempferol 3-(2G-glucosylrutinoside), kaempferol 3-(2″-rhamnosylgalactoside), 7-rhamnoside, kaempferol 3-rhamnosyl-(1->2)-galactoside-7-rhamnoside, luteolin 7-galactosyl-(1->6)-galactoside, orientin 7-O-rhamnoside, 11-hydroperoxy-12,13-epoxy-9-octadecenoic acid, palmitic amide, and 2-hexaprenyl-6-methoxyphenol. The results suggested that reflux was the best technique as compared to ultrasonic and agitation.