A Multi-Channel Frame-Slot Assignment Algorithm for Real-Time MACs in Wireless Sensor Networks

Phan, V.V.,Oh, H. SPRINGER-VERLAG 2014 ICHIT 2012 Vol.8662 No.-

Critical behavior and exponent parameters of the austenitic phase in Ni50−x Pr x Mn37Sn13 alloys with x = 1

Phan, T. L.,Manh, T. V.,Ho, T. A.,Yu, S. C.,Dan, N. H.,Yen, N. H.,Thanh, T. D. Korean Physical Society 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.11

We fabricated Huesler alloy ingots of Ni50-x Pr (x) Mn37Sn13 with x = 0 - 5 by using an arcmelting method. Crystalline-structural analyses revealed the coexistence of austenitic and martensitic phases in the samples with x = 0 and 1, in which the volume fraction of the austenitic phase for x = 1 was higher than that for x = 0. With higher Pr concentrations, x > 1, Pr- and Ni3Sn-related secondary phases, which reduced the magnetic order of the alloys, were formed. Thus, only the sample with x = 1 was more suitable for studying the critical behavior. Based on Landau's phase-transition theory and Banerjee's criteria, we found that this sample undergoes a second-order magnetic phase transition (SOMT) at a temperature around the Curie temperature T (C) a parts per thousand 299 K. Using the modified Arrott plots, asymptotic relations, and a universal scaling law, we determined the values of the critical exponents beta = 0.501 +/- 0.009 and gamma = 1.045 +/- 0.006. These values are very close to those expected for the mean-field theory with beta = 0.5 and gamma = 1, proving the existence of long-range ferromagnetic (FM) order in the sample with x = 1. Particularly, around at temperature T (C) , the magnetic-entropy change reaches the maximum value (a dagger S (max) ). Its magnetic-field dependences can be described by using a power law |a dagger S (max) | ae H (n) , where n = 0.687 is close to the value 0.677 calculated from the theoretical relation n = 1 + (beta - 1)/(beta + gamma). We believe that the doping of a suitable Pr amount in Ni50-x Pr (x) Mn37Sn13 (x a parts per thousand 1) promotes the formation of the austenitic phase and results in long-range FM order. However, the persistence of the martensitic phase and secondary phases favors short-range FM order and thus decreases the FM order in Ni50-x Pr (x) Mn37Sn13.

Improved predictive current control for unbalanced stand-alone doubly-fed induction generator-based wind power systems

Phan, V.-T,Lee, H.-H IET 2011 IET electric power applications Vol.5 No.3

<P>This study proposes an improved predictive current control (PCC) strategy for unbalanced stand-alone doubly-fed induction generator (DFIG)-based wind power systems. The proposed control scheme predicts an appropriate average rotor voltage vector in next switching period to eliminate the rotor current errors in the following control period. The identified voltage vector sequence is then applied to the rotor-side converter (RSC) by using space-vector modulation with constant switching frequency. To increase the control accuracy, a proposed compensation method for the control time delay inherent in the digital implementation, mainly due to the sampling and calculation processes, is adopted. The whole control algorithm is performed in the RSC to achieve the desired control output, that is, compensation for the stator voltage imbalance. In addition, the effect of parameter variation on the performance of the control scheme is also considered. The proposed PCC method was tested by both simulations and experiments with 2.2 kW DFIG feeding an unbalanced load to demonstrate the excellent steady-state performance as well as the extremely fast dynamic response of the proposed current controller.</P>

Stationary frame control scheme for a stand-alone doubly fed induction generator system with effective harmonic voltages rejection

Phan, V-T,Lee, H-H IET 2011 IET electric power applications Vol.5 No.9

<P>A novel stationary frame control scheme for harmonic voltages rejection in a stand-alone doubly fed induction generator (DFIG) with non-linear loads is proposed in this study. The distortion in the stator output voltage of the stand-alone DFIG is mainly because of the non-linear voltage drop in the internal impedance of the generator caused by the non-linear load current. The proposed control scheme directly regulates the instantaneous rotor current in the rotor-side converter (RSC) to reject the fifth and seventh harmonics in the stator output voltage at the point of common coupling (PCC). The main contribution of this study is the development of a novel reference rotor current generator implemented in the stationary reference frame. In this frame, the rotor current controller is developed based on a proportional and three resonant regulators (P3R) that is capable of directly regulating the fundamental, fifth and seventh components of rotor currents without involving decompositions of sequential components. Simulations and experimental results with a 2.2 kW DFIG supplying non-linear loads are presented to demonstrate advanced features of the proposed control scheme.</P>

Extension of the Inhibitory Effect of Chloramphenicol on Bacteria by Incorporating It into Fe3O4 Magnetic Nanoparticles

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.

Development of bioresorbable smart injectable hydrogels based on thermo-responsive copolymer integrated bovine serum albumin bioconjugates for accelerated healing of excisional wounds

V. H. Giang Phan,Thai Minh Duy Le,고피나단 자나르다난,Phuong-Khanh Thi Ngo,이두성,Thavasyappan Thambi 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.96 No.-

One of the major challenges in wound healing is the development of suitable hydrogels that areinjectable, biocompatible with multiple functionalities and properties such as high mechanical, tissueadhesiveness, and swelling properties. However, these hydrogels should not elicit any immunologicalresponse and synthesis steps should be easier and tunable according to the requirements. Consideringthese properties, we synthesized a thermo-sensitive triblock copolymer consisting of bovine serumalbumin (BSA) protein capable of leveraging the needs for a proper wound closure and tissueregeneration on excisional injuries. Firstly, the triblock copolymer consisting of poly(e-caprolactone-colactide)-b-poly(ethylene glycol)-b-poly(e-caprolactone-co-lactide (PCLA) was synthesized and then thecopolymer was grafted with BSA to yield BSA-PCLA bioconjugates. Aqueous solutions of free-flowingbioconjugate sol at room temperature can transform to gel at physiological temperature with highviscoelastic properties. Subcutaneous injection of BSA-PCLA bioconjugate sol into the back of Sprague-Dawley rats formed gel immediately and found to be bioresorbable after 5 weeks without significanttoxicity at implantation sites. BSA-PCLA bioconjugate gel exhibited good adhesive property to majororgans including liver, heart, and spleen when compared with control PCLA gel. When tested for in vivowound closure trials, the BSA-PCLA gels showed rapid wound contraction compared to the PCLA and thecontrol. The increased angiogenesis and collagen deposition were confirmed from the histological studiesof the samples. These highly adhesive, biocompatible, biodegradable, thermos-sensitive bioconjugategels show promising potential in wound healing and tissue regeneration without any additionalbiofactors or inorganic nanoparticles.

Albumin based injectable hydrogel for protein delivery

V.H. Giang PHAN,Doo Sung LEE 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Temperature and pH-sensitive injectable hydrogels based on poly(sulfamethazine carbonate urethane) for sustained delivery of cationic proteins

Phan, V.H. Giang,Thambi, Thavasyappan,Gil, Moon Soo,Lee, Doo Sung Elsevier 2017 Polymer Vol.109 No.-

<P><B>Abstract</B></P> <P>In recent years, protein therapeutics plays a promising role in the field of medicine. However, intrinsic properties of proteins, including short plasma half-life and hydrolytic stability <I>in vivo</I>, are severely limits their application. To surmount these issues, we developed an anionic injectable hydrogel based on temperature- and pH-sensitive poly(ethylene glycol)-poly(sulfamethazine carbonate urethane) (PEG-PSMCU) copolymers for the sustained delivery of cationic model protein, lysozyme. The PEG-PSMCU copolymers exhibit pH and temperature-induced sol-to-gel phase transition in aqueous solutions. The mechanical properties of PEG-PSMCU copolymers, such as viscosity, gelation rate, and mechanical strength, were controllably tunable by varying the polymer weight, pH and temperature. An <I>in vitro</I> biocompatibility test indicated that PEG-PSMCU-based copolymers, even at high polymer concentrations (up to 2000 μg/ml), was not toxic to fibroblast cells. The <I>in vivo</I> gel formation was confirmed by subcutaneous injection of PEG-PSMCU-based copolymer solutions (20 wt%) into Sprague-Dawley (SD) rats, which indicated in situ gel formation with uniform porous structure. Furthermore, an <I>in vivo</I> biodegradation study of the PEG-PSMCU anionic hydrogels showed a surface-controlled degradation of the gel matrix. Lysozyme, chosen as a cationic model protein, was loaded into an anionic hydrogel through ionic and hydrophobic interactions. Lysozyme-loaded PEG-PSMCU copolymers readily formed an in situ hydrogel after subcutaneous injection in SD rats, which markedly retarded the initial burst and led to the sustained release of lysozyme for 7 days. Overall, injectable anionic hydrogels prepared in this study can act as a localized hydrogel depot of cationic proteins, which inhibited initial burst while facilitating sustained release, and open a new paradigm for sustained delivery of cationic proteins.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Temperature- and pH-sensitive PEG-PSMCU copolymer was synthesized and characterized. </LI> <LI> PEG-PSMCU copolymers could form in situ hydrogel in SD rats. </LI> <LI> PEG-PSMCU hydrogels exhibited sustained biodegradation <I>in vivo.</I> </LI> <LI> Lysozyme-loaded PEG-PSMCU hydrogels exhibit sustained protein release <I>in vivo.</I> </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>An anionic injectable hydrogel based on temperature- and pH-sensitive poly(ethylene glycol)-poly(sulfamethazine carbonate urethane) copolymers has been developed for the sustained delivery of cationic model protein, lysozyme.</P> <P>[DISPLAY OMISSION]</P>

향상된 수동 날개 회전을 갖는 곤충 모방 날갯짓 장치

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.

Magnetic and magnetocaloric properties of Sm_1−xCa_xMnO₃ (<i>x</i> =0.88) nanoparticles

Phan, T.L.,Dang, N.T.,Ho, T.A.,Rhyee, J.S.,Shon, W.H.,Tarigan, K.,Manh, T.V. North-Holland Pub. Co 2017 Journal of magnetism and magnetic materials Vol.443 No.-

<P><B>Abstract</B></P> <P>We used the mechanical milling to prepare orthorhombic Sm<SUB>0.12</SUB>Ca<SUB>0.88</SUB>MnO<SUB>3</SUB> samples with the average crystallite size (<I>d</I>) changing from 100 to 139nm. Their magnetic and magnetocaloric properties were then studied upon magnetization data versus the temperature and magnetic field, <I>M</I>(<I>T</I>, <I>H</I>). The results revealed the samples undergoing the ferromagnetic-paramagnetic (FM-PM) phase transition at the Curie temperature <I>T</I> <SUB>C</SUB> ≈110K. Around this transition, the magnetic-entropy change (Δ<I>S</I> <SUB>m</SUB>) reaches the maxima. The maximum |Δ<I>S</I> <SUB>m</SUB>| values are about 2–4J·kg<SUP>−1</SUP>·K<SUP>−1</SUP>, corresponding to relative cooling power of 35–60J·kg<SUP>−1</SUP>, for an applied field <I>H</I> =30kOe. The assessments based on Banerjee’s criteria and constructing a universal curve for |Δ<I>S</I> <SUB>m</SUB>(<I>T</I>, <I>H</I>)| data indicate the samples having the nature of a second-order phase transition. Also, the detailed analyses based on the Curie-Weiss law and magnetic-order exponent prove the existence of the Griffiths phase and magnetic inhomogeneity in the samples. These properties would be changed by changing <I>d</I>.</P>