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H.V. Phan,Q.V. Nguyen,H.C. Park(박훈철),N.S. Goo(구남서),D.Y. Byun(변도영) 한국항공우주학회 2011 한국항공우주학회 학술발표회 논문집 Vol.2011 No.11
본 연구에서는 날갯짓 장치의 개선을 위하여, 날개를 유연 힌지 없이 직접 날갯짓 기구에 연결하고, 날개 뿌리 부분의 날개 뒷전을 날갯짓 장치 몸체에 연결함으로써, 날갯짓 동안 날개가 반능동적으로 날개 회전이 발생하도록 하였다. 이로써 날개 뿌리에서는 날개 회전이 적고 끝단 끝단에서는 날개 회전이 크도록 하여, 실제 장수풍뎅이의 날갯짓 궤적과 유사하게 하였다. 사전 연구에서 개발한 swing test 장치를 이용하여 수정된 날갯짓 장치의 추력을 측정한 결과, 수정된 날갯짓 장치는 유연 힌지를 갖는 이전의 날갯짓 장치보다 10% 이상 더 큰 추력이 발생함을 확인하였다. 이로써 반자동 날개 회전이 추력을 향상하는데 효과적임을 입증하였다. In this work, we modified the previous flapping-wing system such that it can produce higher force. The wings were directly connected to the output links of the flapping mechanism without flexible hinges. Instead, the trailing edges of the wings near wing root were connected to the body, so that the wings can create semi-active wing rotation. Consequently, the wing rotation angle becomes variable from the wing root to wing tip during flapping. Threedimensional wing kinematics was measured by using two high-speed cameras and compared it with that of the previous flapping-wing with similar wing span, wing area, and flapping frequency. We also measured the thrust by using the swing test method. The measured thrust of the modified flapping-wing system is more than 10% higher than that of the previous one. Thus, the semi-active wing rotation mechanism is proven to improve thrust production.
H. T. Khuat,N. H. Hai,C. V. Thach,N. Chau,T. N. Phan,V. T. Nguyen 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Magnetite Fe$_3$O$_4$ nanoparticles were prepared by using a co-precipitation method, then functionalized by double layers of surfactants (core/oleic acid (OA)/sodium dodecyl sulfate (SDS)). For application as a drug carrier, the double-layer-coated magnetic nanoparticles were fully loaded with the antibiotic chloramphenicol (Cm) to investigate the effect of the drug release process on the bacteria {\it Escherichia coli} (E. coli). The water-soluble Cm and Cm-coated magnetic nanoparticles (Cm-NPs) (equivalent to 50 $\mu$l of 5 -- 200 $\mu$g/ml Cm) were poured into small holes on agar plates spread with E. coli, after which the plates were incubated overnight. The diameters of the non-bacteria circles were shown to gain their maximal values after 14 h, then to gradually decrease in almost all samples. Nevertheless, the circles created by Cm-NPs were about 1.5 times larger than those for the control Cm. The speed of bacterial lawn re-grown in the case of the Cm-NPs was obviously slower than that of the controlled Cm. We conclude that the magnetic nanoparticles gradually release the antibiotic, thereby maintaining the stability and the effect of the antibiotic longer than that of the conventional water-soluble antibiotic.
Yen H. Vo,Thanh V. Le,Hieu D. Nguyen,Tuong A. To,Hiep Q. Ha,Anh T. Nguyen,Anh N.Q. Phan,Nam T.S. Phan 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.64 No.-
Zirconium-based metal-organic framework MOF-808 was synthesized, and sulfated with aqueous sulfuric acid. Sulfated MOF-808 was utilized as a recyclable heterogeneous catalyst for the synthesis of quinazolinones from β-ketoesters and benzamides, and for the synthesis of benzimidazoles from β-ketoesters and o-phenylenediamines in glycerol as a green solvent. The sulfated MOF-808 catalyst was more active than many heterogeneous and homogeneous catalysts. The combination of the sulfated MOF-808 and glycerol was also effective for the reaction of o-aminothiophenols with β-diketones or cyclic β-diketones to produce benzothiazoles. To our best knowledge, MOF-based catalysts were not previously utilized as heterogeneous catalyst in glycerol as green solvent.
Numerical study of the indentation formation of a compound droplet in a constriction
Hoe D. Nguyen,Truong V. Vu,Phan H. Nguyen,Binh D. Pham,Nang X. Ho,Cuong T. Nguyen,Vinh T. Nguyen 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.4
A compound droplet deforming in a constricted tube widely appears in drug delivery and microfluidic devices. In such a constriction, an indentation can present at the trailing surface of the droplet. However, this aspect has not been fully investigated and understood so far. This study focuses on the effects of some dimensionless parameters on the negative curvature, i.e., indentation, at the trailing surface of a compound droplet moving through a constricted tube. The presence of the constriction at the middle of the tube length enhances the droplet indentation. Numerical results were obtained for the capillary number Ca (varied in range of 0.1 - 1.0), the inner-to-outer droplet radius ratio R 21 (varied in range of 0.2 - 0.9), the droplet-to-tube radius ratio R 10 (varied in range of 0.2 - 0.9), the inner-to-outer interfacial tension coefficient ratio σ 21 (varied in range of 0.1 - 6.4), and the normalized depth of the constriction d/R (varied in range of 0.0 - 0.8). The results reveal that the most influencing factor is Ca, increasing its value leads to the increment of the maximum indentation at the trailing surface of the inner and outer droplets. The indentation is also increased with increasing the value of R 10and d/R. In contrast, increasing R 21 results in a decrease in the indentation at the trailing surface of the outer droplet. When increasing σ 21 , the indentation at the trailing surface of the inner one is quickly suppressed, while the outer droplet is minorly affected. We also point out the patterns of the trailing surface of the inner and outer droplets and their transitions from one to the other patterns in the diagrams based on these parameters.
Khoa D. Nguyen,Son H. Doan,Anh N.V. Ngo,Tung T. Nguyen,Nam T.S. Phan 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.44 No.-
A metal–organic framework Fe3O(BPDC)3 was synthesized, and used as a productive heterogeneouscatalyst for the direct C–N coupling of azoles with ethers via oxidative C–H activation to produce azolederivatives. The MOF-based catalyst displayed higher catalytic efficiency than many homogeneouscatalysts as well as several MOFs in the transformation. The MOF-based catalyst could be reused manytimes for the synthesis of azole derivatives by the direct C–N coupling of azoles with ethers without anoteworthy deterioration in catalytic efficiency. To the best of our knowledge, this direct C–N couplingreaction was not previously performed in the presence of heterogeneous catalysts.
Khang X. Nguyen,Phuc H. Pham,An C.D. Nguyen,Chuc T. Nguyen,Tung T. Nguyen,Phong D. Tran,Nam T.S. Phan 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.92 No.-
A Fe-Mo-Se nanopowder, synthesized by a solvothermal protocol, was utilized as a heterogeneouscatalyst for the synthesis of 2-arylquinazolines from DL-α-phenylglycine-based α-amino acids and2-nitrobenzyl alcohols via domino transformations. High yields and selectivity were achieved undersolvent-free conditions. The Fe-Mo-Se catalyst offered considerably higher activity than numeroushomogeneous and heterogeneous catalysts. To our best knowledge, this domino reaction is new, and theutilization of iron-molybdenum selenide catalyst in the synthesis of quinazolines was not previouslyreported.
T. L. Phan,Nguyen H.H.,Jeong W.H.,Idczak R.,Tran V.H.,Yang D.S.,Lee B.W. 한국물리학회 2021 Current Applied Physics Vol.29 No.-
Polycrystalline SrCo1⋅2Fe10⋅8O19 (SCFO) and SrMn1⋅2Fe10⋅8O19 (SMFO) samples were prepared by the normal ceramic technique. Powder X-ray diffraction patterns indicated the crystallization in the M-type hexaferrite structure of the samples. X-ray absorption analyses proved Co2+ and Mn3+,4+ ions existing in SCFO and SMFO, respectively. Though Fe3+ is dominant in both the compounds, small amounts of Fe2+ and Fe4+ are present in SCFO and SMFO, respectively. M¨ossbauer spectra analyses also confirmed the dominance of Fe3+ in both the samples. Additionally, Fe3+ ions in the 12 k, 4f1, 4f2, and 2a sites could be attributed to the high-spin state (S = 5/2). A large QS value for the sextet assigned to the 2b site indicated that in this case Fe3+ could be in the lowspin state (S = 1/2) or there was the addition of Fe2+ (or Fe4+) when Fe in SrFe12O19 was partially replaced by Co2+ (or Mn3+,4+). The mixture of transition-metal ions with different oxidation states influenced the magnetic properties and microwave shielding ability. At frequencies f = 10–18 GHz, we have found SCFO showing the lowest reflection loss with RL = 11.1 dB at 13.2 GHz and the thickness t = 2.2 mm. With an absorption bandwidth of 0.7 GHz, and about 92% microwave energy being absorbed, SCFO is considered as a potential candidate for microwave shielding applications.
Thermocapillary migration of a fluid compound droplet
Vinh T. Nguyen,Truong V. Vu,Phan H. Nguyen,Nang X. Ho,Binh D. Pham,Hoe D. Nguyen,Hung V. Vu 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.9
Compound and simple droplets have been studied and appeared in many life applications, e.g., drug processing and microfluidic systems. Many studies have been conducted on the thermocapillary effects on simple droplets, but similar studies on compound droplets are quite rare. Filling this missing gap, this paper presents the front-tracking-based simulation results of the thermocapillary effects on compound droplets in a certain limited domain. The compound droplet consists of a single inner core that is initially concentric with the outer one. Various dimensionless parameters including Reynolds number from 1 to 50, Marangoni number from 1 to 100, droplet radius ratio from 0.3 to 0.8, and viscosity ratios from 0.1 to 6.4 are varied to reveal their influences on the migration of a compound droplet from cold to hot regions. Initially, the inner droplet moves faster than the outer one, and when the leading surface of the inner droplet touches the outer one, the inner and outer droplets migrate at the same speed. The effects of these parameters on the compound droplet eccentricity are also considered.