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Duy, Le Thai,Lee, Gyuyeon,Kim, Jinseo,Ahn, Byungmin,Cho, In Sun,Yu, Hak Ki,Seo, Hyungtak Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.774 No.-
<P><B>Abstract</B></P> <P>Detection of hydrogen (H<SUB>2</SUB>) over a wide concentration range (from parts-per-million levels to 4%) is necessary for safety in using hydrogen-fuel cell systems. For this purpose, our development of H<SUB>2</SUB> sensitive nanohybrids of reduced graphene oxide (rGO) and chemochromic palladium-decorated molybdenum trioxide (Pd:MoO<SUB>3</SUB>) nanoflakes is presented. Additionally, the nanohybrids were employed as the active channel in a thin film transistor platform to invest informative characteristics for understanding their electrical properties and sensing mechanism. Through sensing measurements, (i) phenomena relating to response saturation and reversed behavior of gas sensors towards high exposure doses (i.e., p-to-n transition) and (ii) doping effects on the p-to-n transition and detection range of the hybrid materials are clarified. With combining electrical and visual output signals, the bimodal devices using the hole-doped nanohybrids can detect H<SUB>2</SUB> over a wide concentration range (from 10 ppm to over 10%) at room temperature. Our results reveal opportunities for further development and improvement of hybrid nanomaterials and chemical sensors having a large sensing capability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Our nanohybrids have two sensing capabilities towards hydrogen. </LI> <LI> Transistor sensors provide information for understanding phenomena and mechanism. </LI> <LI> Effect of hole-doping on the detection range is explored. </LI> <LI> The bimodal sensors can detect hydrogen from 10 ppm to over 10%. </LI> <LI> Transition from p-to n-type behavior of the nanohybrid can cause its response saturation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Duy, Le Thai,Kalanur, Shankara S.,Cho, In Sun,Seo, Hyungtak Elsevier 2018 Materials chemistry and physics Vol.218 No.-
<P><B>Abstract</B></P> <P>Deoxygenation of graphene oxide is a low-cost and effective way to yield graphene (i.e., reduced graphene oxide - RGO) for many applications. However, choices of reduction approach and reduction time need consideration due to damaging pre-existing materials on electronic devices. Here, we found a facile and eco-friendly route that was based on the photo-oxidation of ethanol (diluted in water) on a catalytic TiO<SUB>2</SUB> film to rapidly induce the formation of RGO within 15 min under UV (20 mW/cm<SUP>2</SUP>) or sun lights (1 sun = 100 mW/cm<SUP>2</SUP>). Our reduction route was indirectly activated by chain reactions of ethanol and TiO<SUB>2</SUB> (so-called domino effect) because the GO deoxygenation occurred even when the samples were placed around and not in contact with TiO<SUB>2</SUB> film. To obtain the highest reduction, the samples should stay on the catalytic film to receive lights for activation and acceleration of reactions. Furthermore, effects of exposure time (1–20 min), ethanol concentration (14.3–100%), and light intensity on RGO quality explored with the use of chemiresistive devices. The results of demonstrative sensing measurements towards NO<SUB>2</SUB> and NH<SUB>3</SUB> indicate that our method is promising for electrical applications using solution processable RGO.</P> <P><B>Highlights</B></P> <P> <UL> <LI> RGO can be rapidly formed through ethanol photolysis. </LI> <LI> Sunlight is used for activating and accelerating chain reactions. </LI> <LI> The reduction route is not based on the direct charge transfer between GO and TiO<SUB>2</SUB>. </LI> <LI> The domino effect of catalysis is promising for exploring further applications. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>An economical and rapid approach to reduce graphene oxide is developed for electronic applications. It is based on a domino effect that can extend the function as well as possible applications of a catalyst.</P> <P>[DISPLAY OMISSION]</P>
Le, Thai Minh Duy,Duong, Huu Thuy Trang,Thambi, Thavasyappan,Giang Phan, V.H.,Jeong, Ji Hoon,Lee, Doo Sung American Chemical Society 2018 Biomacromolecules Vol.19 No.8
<P>Despite great potential, the delivery of genetic materials into cells or tissues of interest remains challenging owing to their susceptibility to nuclease degradation, lack of permeability to the cell membrane, and short in vivo half-life, which severely restrict their widespread use in therapeutics. To surmount these shortcomings, we developed a bioinspired in situ-forming pH- and temperature-sensitive injectable hydrogel depot that could control the delivery of DNA-bearing polyplexes for versatile biomedical applications. A series of multiblock copolymer, comprised of water-soluble poly(ethylene glycol) (PEG) and pH- and temperature-responsive poly(sulfamethazine ester urethane) (PSMEU), has been synthesized as in situ-forming injectable hydrogelators. The free-flowing PEG-PSMEU copolymer sols at high pH and room temperature (pH 8.5, 23 °C) were transformed to stable gel at the body condition (pH 7.4, 37 °C). Physical and mechanical properties of hydrogels, including their degradation rate and viscosity, are elegantly controlled by varying the composition of urethane ester units. Subcutaneous administration of free-flowing PEG-PSMEU copolymer sols to the dorsal region of Sprague-Dawley rats instantly formed hydrogel depot. The degradation of the hydrogel depot was slow at the beginning and found to be bioresorbable after two months. Cationic protein or DNA-bearing polyplex-loaded PEG-PSMEU copolymer sols formed stable gel and controlled its release over 10 days in vivo. Owing to the presence of urethane linkages, the PEG-PSMEU possesses excellent adhesion strength to wide range of surfaces including glass, plastic, and fresh organs. More importantly, the hydrogels effectively adhered on human skin and peeled easily without eliciting an inflammatory response. Subcutaneous implantation of PEG-PSMEU copolymer sols effectively sealed the ruptured skin, which accelerated the wound healing process as observed by the skin appendage morphogenesis. The bioinspired in situ-forming pH- and temperature-sensitive injectable adhesive hydrogel may provide a promising platform for myriad biomedical applications as controlled delivery vehicle, adhesive, and tissue regeneration.</P> [FIG OMISSION]</BR>
Safety assessment of an underground tunnel subjected to missile impact using numerical simulations
Duc-Kien Thai,Duy-Liem Nguyen,Thanh-Tung Pham,Thai-Hoan Pham 사단법인 한국계산역학회 2021 Computers and Concrete, An International Journal Vol.27 No.1
This work presents a safety assessment of an underground tunnel subjected to a ballistic missile attack employing the numerical approach. For the impact simulation, a box shaped reinforced concrete (RC) structure with a cross section dimension of 8.0×10.0 m under a soil layer that was attacked by a SCUD missile was modeled using finite element (FE) software LS-DYNA. SCUD missile is one of a series of tactical ballistic missiles developed by Soviet Union during the Cold War, which is adopted for a short-range ballistic missile. The developed FE simulation for the penetration depth of the missile impacting into the soil structure was verified from the well-known formula of the penetration prediction. The soil-structure interaction, the soil type, and the impact missile velocity effects on the penetration depth of the missile into the different soil types were investigated. The safety assessment of the underground tunnel was performed with regard to the different depths of the underground tunnel. For each missile velocity and soil type, a specific depth called the unsafe depth was obtained from the analysis results. The structure beneath the soil beyond this depth remains safe. The unsafe depth was found to be increased with the increasing missile velocity.
Empirical evaluations for predicting the damage of FRC wall subjected to close-in explosions
Duc-Kien Thai,Thai-Hoan Pham,Duy-Liem Nguyen,Tran Minh Tu,Phan Van Tien 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.49 No.1
This paper presents a development of empirical evaluations, which can be used to evaluate the damage of fiberreinforced concrete composites (FRC) wall subjected to close-in blast loads. For this development, a combined application of numerical simulation and machine learning approaches are employed. First, finite element modeling of FRC wall under blast loading is developed and verified using experimental data. Numerical analyses are then carried out to investigate the dynamic behavior of the FRC wall under blast loading. In addition, a data set of 384 samples on the damage of FRC wall due to blast loads is then produced in order to develop machine learning models. Second, three robust machine learning models of Random Forest (RF), Support Vector Machine (SVM), and Extreme Gradient Boosting (XGBoost) are employed to propose empirical evaluations for predicting the damage of FRC wall. The proposed empirical evaluations are very useful for practical evaluation and design of FRC wall subjected to blast loads.
Hoa Hong Pham,Ngoc Thai Pham,Duy Vu Nguyen 글로벌지식마케팅경영학회 2016 Global Marketing Conference Vol.2016 No.7
Although country-of-origin has been a controversial topic in literature, there has been little research effort to explain the nature linkage between country-of-origin and perceived quality from consumers in emerging markets. Drawing on the notion of country-of-origin, this study proposes the concept of product-country-image which is operationalized with the three components of cognitive, affective and conative. Structural equation modeling is employed to explore the relationship between the product-country-image and perceived quality. The findings indicate that only ‘affective components’ are positively related to ‘conative components’ among three pairs. What is more, structural equitation modeling demonstrated that the influence of product-country image on perceived quality is simultaneously regardless of the level of consumers’ familiarity with a foreign country’s product. Using data collected from 348 Vietnamese consumers, this study generates new insights for academics and practitioners.