Modeling of parallel power MOSFETs in steady-state

In high-power applications, multiple power MOSFETs are connected in parallel and treated as a single switch in order to handle much larger total currents. In this paper, a parallel power MOSFETs model from the turnoff state until they reach their steady state is introduced. The model represents the relationship between each power MOSFET's gate voltage and the current distribution among them. The study's key purpose is to use the model for dealing with the asymmetry in sharing current and power loss between these semiconductor devices during the steady state region.Comment: 10 pages, 7 figures, The 2023 INTERNATIONAL SYMPOSIUM ON ADVANCED ENGINEERING (ISAE2023

Ecological Engineering and Restoration of Eroded Muddy Coasts in South East Asia: Knowledge Gaps and Recommendations

Ecological engineering (EE) was employed for developing strategies for stabilizing eroded muddy coasts (EMCs). However, there was a limited analysis of these EE strategies with respect to design, performance, and lessons learned. This study employed a critical review for addressing the limitations. There were four EE models designed with different restoration interventions for stabilizing EMCs. The models using active interventions have not been cost-effective in controlling erosion because the interventions failed to achieve their goals or were costly and unnecessary. Of the two passive intervention models, the one with structures constructed from onshore proved to be more cost-effective in terms of construction costs, the survival rate of transplanted seedlings, and levels of sea mud accumulation. Interventions with adequate consideration of the muddy coastal ecological processes and the ecological reasoning for the positioning of these interventions play a crucial role in stabilizing EMCs. A passive restoration model using gradually expanded interventions should be promoted in order to ensure sustainable management of EMCs in the future

No Evidence for Evolution in the Far-Infrared-Radio Correlation out to z ~ 2 in the eCDFS

We investigate the 70 um Far-Infrared Radio Correlation (FRC) of star-forming galaxies in the Extended Chandra Deep Field South (ECDFS) out to z > 2. We use 70 um data from the Far-Infrared Deep Extragalactic Legacy Survey (FIDEL), which comprises the most sensitive (~0.8 mJy rms) and extensive far-infrared deep field observations using MIPS on the Spitzer Space Telescope, and 1.4 GHz radio data (~8 uJy/beam rms) from the VLA. In order to quantify the evolution of the FRC we use both survival analysis and stacking techniques which we find give similar results. We also calculate the FRC using total infrared luminosity and rest-frame radio luminosity, qTIR, and find that qTIR is constant (within 0.22) over the redshift range 0 - 2. We see no evidence for evolution in the FRC at 70 um which is surprising given the many factors that are expected to change this ratio at high redshifts.Comment: 18 pages, 13 figures. Accepted for publication in Ap

Green Tribology

This chapter provides an overview of Green tribology, which is a new direction in the development of tribology, a new interesting area for scientific researches and a new way to turn tribology into a friend of ecological environment and saving energy. Green tribology is considered as well as close area with other “green” disciplines like green engineering and green chemistry. In the chapter, the various aspects of green tribology such as the concept, perspectives, role and goal, main principles, primary areas, challenges and directions of the future development have been discussed. It was clarified that green tribology can be defined as an interdisciplinary field attributed to the broad induction of various concepts such as energy, materials science, green lubrication, and environmental science. The most important role and goal of green tribology is improvement of efficiency by minimizing wear and friction in tribological processes to save energy, resources and protect environment, and consequently, improve the quality of human life. The twelve principles and three areas of green tribology were analyzed. Observation of these principles can greatly reduce the environmental impact of tribological processes, assist economic development and, as a result, improve the quality of life. The integration of these areas remains the major challenge of green tribology and defines the future directions of research in this field. This work also presents a rather detailed analysis of the most important effect in green tribology—the “zero-wear” effect (selective transfer effect). It was established that the “zero-wear” effect is due to self-organization in frictional interaction in tribological systems, which is the consequence of the complex tribo-chemical reactions and physico-chemical processes occurred in the area of frictional contact, that lead to the manifestation of unique tribological characteristics: super-antifrictional (friction coefficient ~ 10−3) and without wear (intensity wear ~10−15). This condition of tribo-system was provided by a protective nanocrystalline servovite film made of soft metal with unusual combination of mechanical properties

Sand Spit Morphology at an Inlet on Phu Quoc Island, Vietnam

Tidal inlets with attached sand spits are a very common coastal landform. Since the evolution of sand spits along coastlines influence the social-economic development of local coastal areas, sand spits have become the objects of numerous studies. However, previous studies have mainly focused on sand spits that are usually in the scale of hundreds of meters in width, whilst knowledge about the evolution of smaller-scale sand spits still remains limited. Therefore, in this study, the morphological change of a small and unexplored sand spit in front of Song Tranh Inlet on the west coast of Phu Quoc Island, Vietnam is investigated. Satellite images are first used to observe the morphological change of the sand spit and calculate the longshore sediment transport rates (LSTR) along the sand spit. Waves and beach sediments are collected at the study site to calculate the longshore sediment transport rate using the CERC formula. It is found that there is a seasonal variation in the evolution of the sand spit at Song Tranh Inlet. The longshore sediment transport rates along the spit calculated by image analysis are 39,000 m$^3$/year, 66,000 m$^3$/year, and 40,000 m$^3$/year, whilst the longshore sediment transport rate calculated by the CERC formula is 72,000 m$^3$/year. This study aims to contribute to the methodology for investigating the evolutions of small sand spits and, specifically, sustainable coastal management for Phu Quoc Island, which is well-known as the Pearl Island of Vietnam

Antibacterial hydrogel containing Piper betle L. extract for acne treatment, an ex vivo investigation

The current treatments of acne vulgaris and acne-like disorders such as gram-negative folliculitis possess lots of unwanted side effects. Thus, alternative approach of utilizing natural plant extracts, specifically Piper betle L., have gained much attention. To this end, this work developed, characterized, and ex vivo evaluated novel antibiotics hydrogels containing P. betle L. leaf extract for acne treatment. Firstly, the design of experiments (DoE) D-optimal method was successfully developed, optimized, and validated, to investigate the relationship between P. betle L. extraction conditions and the extract properties. Secondly, the best extract was encapsulated in the hydrogel formulations composed of carbopol 940, propylene glycol, and cocamidopropyl betaine. Finally, the hydrogel was ex vivo determined its antibacterial activity on bacteria isolated from 15 patient acne samples. The optimal extraction condition being an extraction solvent/plant weight ratio of 4.034:1, an extraction time of 2.147 h, and a water extract volume of 91.4 mL. This condition yielded an extract total phenolic content of 3.337±0.034 g GAE/g, and minimum inhibitory concentrations of 32 µg/mL and 128 µg/mL on Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922, respectively. The hydrogel possessed suitable properties for a topical medication, including a viscosity of 6800 cps, a pH of 7.0, and a good foaming ability, at both 10°C, 25°C, and 40°C. The hydrogel showed higher antibacterial activity than the positive controls in both gram-positive and gram-negative bacteria. Conclusively, the hydrogel could become a potential pharmaceutical product for acne treatment

PRELIMINARY STUDY OF THE ANTIOXIDANT PROPERTIES OF OPHIOCORDYCEPS SOBOLIFERA

The aim of study was to determine preliminary phytochemical analysis and the antioxidant potential of Ophiocordyceps sobolifera. The antioxidant activity of Ophiocordyceps sobolifera was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and total antioxidant activity methods. Phytochemical analyses revealed the presence of steroids, triterpenoids, alkaloids, phenolics, flavoinods, protein, carbohydarte and saponins. The antioxidant activity of the ethanol extracts and water extracts showed high antioxidant activity with the lowest half maximal inhibitory concentration (IC50) values to 0.70 from 0.95mg/mL, realtively. Total antioxidant capacity of the O. sobolifera showed contained from 5.52 ± 0.14 to 12,71 ± 0.23 mg GA/g or from 3.55 ± 0.15 to 7.87 ± .05 μmol AS/g. These data suggest that O. sobolifera is a natural source of antioxidants

Vietnam geographical exploitation under the United Nations Convention on the Law of the Sea in 1982 (UNCLOS 1982)

As an active member of the United Nations Convention on the Law of the Sea - UNCLOS, Vietnam has completed 3 Reports on the Limits of the Continental Shelf and has submitted two of them to the Commission on the Limits of the Continental Shelf - CLCS, before the deadline 13-5-2009. Those are: (1) Outer Limits of the Vietnam’s Extended Continental Shelf: North Area (VNM-N); (2) Outer Limits of the Vietnam’s Extended Continental Shelf: Middle Area (VNM-M) and (3) Vietnam - Malaysia Joint Continental Shelf Submission. The VNM-M has not yet been submitted but it was mentioned to the CLCS and will be submitted in the appropriate time.Vietnam’s submissions were highly appreciated by CLCS; although the CLCS has not yet organized a special sub-committee to look at our reports, the secretariat of CLCS has already posted the executive reports of our submissions, with our principle claims on the continental shelf, on the website of the CLCS since May 2009. This paper presents shortly the UNCLOS and its application in Vietnam case

The mitochondrial genomes of the ciliates Euplotes minuta and Euplotes crassus

Contains fulltext : 75729.pdf (publisher's version ) (Open Access)BACKGROUND: There are thousands of very diverse ciliate species from which only a handful mitochondrial genomes have been studied so far. These genomes are rather similar because the ciliates analysed (Tetrahymena spp. and Paramecium aurelia) are closely related. Here we study the mitochondrial genomes of the hypotrichous ciliates Euplotes minuta and Euplotes crassus. These ciliates are only distantly related to Tetrahymena spp. and Paramecium aurelia, but more closely related to Nyctotherus ovalis, which possesses a hydrogenosomal (mitochondrial) genome. RESULTS: The linear mitochondrial genomes of the hypotrichous ciliates Euplotes minuta and Euplotes crassus were sequenced and compared with the mitochondrial genomes of several Tetrahymena species, Paramecium aurelia and the partially sequenced mitochondrial genome of the anaerobic ciliate Nyctotherus ovalis. This study reports new features such as long 5'gene extensions of several mitochondrial genes, extremely long cox1 and cox2 open reading frames and a large repeat in the middle of the linear mitochondrial genome. The repeat separates the open reading frames into two blocks, each having a single direction of transcription, from the repeat towards the ends of the chromosome. Although the Euplotes mitochondrial gene content is almost identical to that of Paramecium and Tetrahymena, the order of the genes is completely different. In contrast, the 33273 bp (excluding the repeat region) piece of the mitochondrial genome that has been sequenced in both Euplotes species exhibits no difference in gene order. Unexpectedly, many of the mitochondrial genes of E. minuta encoding ribosomal proteins possess N-terminal extensions that are similar to mitochondrial targeting signals. CONCLUSION: The mitochondrial genomes of the hypotrichous ciliates Euplotes minuta and Euplotes crassus are rather different from the previously studied genomes. Many genes are extended in size compared to mitochondrial genes from other sources