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      • Seroprevalence of Toxoplasma gondii and Trichinella spiralis infections in wild boars (Sus scrofa) in Korea

        Kang, S.W.,Doan, H.T.T.,Noh, J.H.,Choe, S.E.,Yoo, M.S.,Kim, Y.H.,Reddy, K.E.,Nguyen, T.T.D.,Van Quyen, D.,Nguyen, L.T.K.,Kweon, C.H.,Jung, S.C. Elsevier 2013 Parasitology international Vol.62 No.6

        Toxoplasma gondii and Trichinella spiralis are important zoonotic pathogens with worldwide distributions. In Korea, several outbreaks of human toxoplasmosis and trichinellosis due to the consumption of infected wild animals have been reported. The purpose of this study was to determine the seroprevalence of T. gondii and T. spiralis infections in wild boars killed in Korea from December 2009 to October 2011. A total of 521 wild boars hunted in eight provinces were examined for antibodies to T. gondii and T. spiralis by using commercial ELISA kits. Overall, 25.1% of serum samples from individual boars were seropositive for T. gondii and 1.7% were seropositive for T. spiralis. Seropositive for T. gondii was found in the boars in all the eight provinces investigated and for T. spiralis in four provinces. This is the first report on the seroprevalence of T. gondii and T. spiralis infections in wild boars in Korea. The consumption of undercooked wild boar meat may expose humans to a high risk of infection.

      • Inhomogeneous Ferromagnetism and Spin-Glass-Like Behavior in <inline-formula> <tex-math notation='TeX'> <tex> $({\rm Nd}_{1-x}{\rm Y}_{x})_{0.7}{\rm Sr}_{0.3}{\rm MnO}_{3}$ </tex> </tex-math></inline-formula> With <inline-formula> <tex-math notation='TeX

        Phan, T. L.,Nguyen, V. D.,Ho, T. A.,Khiem, N. V.,Thanh, T. D.,Phuc, N. X.,Thang, P. D.,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.6

        <P>The magnetic properties of polycrystalline ceramic samples (Nd1-xYx)(0.7)Sr0.3MnO3 with x = 0.21 - 0.35 were studied by means of dc magnetization and ac susceptibility measurements. Experimental results reveal a strong decrease of the ferromagnetic (FM)-paramagnetic phase-transition temperature (T-C) from 97 to 65 K as increasing x from 0.21 to 0.35, respectively. There is magnetic inhomogeneity associated with short-range FM order. Particularly, the samples undergo a spin-glass (SG) phase transition at the so-called blocking temperature (T-B) below T-C, which shifts toward lower temperatures with increasing the applied field, Hex; T-B -> T-g (the SG phase-transition temperature) as H-ex -> 0. The existence of the SG behavior in these samples was also confirmed by frequency (f) dependences of the ac susceptibility. For the in-phase/real component, chi' (T), it shows a frequency-dependent peak at the SG freezing temperature (T-f); T-f -> T-g as f -> 0. Dynamics of this process were analyzed by means of the slowing down scaling law, tau/tau(0) proportional to (T-f/T-g - 1)(-zv), where tau(0) and zv are the characteristic time and critical exponent, respectively. Fitting the experimental T-f(f) data to the scaling law gave the results of zv = 10.1-12.3 and tau(0) = 10(-21)-10(-15)s. These values are different from those expected for canonical SG systems with zv = 10 and tau(0) = 10(-13)s, revealing the cluster-SG behavior of (Nd1-xYx)(0.7)Sr0.3MnO3 samples. Notably, the increase in Y content leads to the shift of tau(0) and zv values toward those of canonical SG systems, which is ascribed to an expansion of SG clusters.</P>

      • Magnetocaloric Effect and Critical Behavior of <inline-formula> <tex-math notation='TeX'> <tex> ${\rm Ni}_{42}{\rm Ag}_{8}{\rm Mn}_{37}{\rm Sn}_{13}$ </tex> </tex-math></inline-formula> Alloys

        Tran Dang Thanh,Phan, T. L.,Pham Thi Thanh,Nguyen Hai Yen,Nguyen Huy Dan,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.4

        <P>This paper presents the magnetocaloric effect and critical behavior of alloy ingot and ribbon samples of Ni<SUB>50</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> doped with 8% Ag, which were prepared by an arc-melting and rapidly quenched melt-spinning methods, respectively. Experimental results reveal that a partial replacement of Ag for Ni leads to stamping out the antiferromagnetic martensitic phase. This means that there is only the austenitic phase with a ferromagnetic-paramagnetic (FM-PM) phase-transition temperature of T<SUB>C</SUB> ≈ 295 K. Detailed studies and analyses around the phase transition region prove both samples undergoing a second-order magnetic phase transition. Basing on magnetic field dependences of magnetization, we have determined the magnetic-entropy change (ΔS<SUB>m</SUB>) of the samples. Under a field change of 10 kOe, the maximum magnetic-entropy change (|ΔS<SUB>max</SUB>|) reaches values 0.54 and 0.69 J · kg<SUP>-1</SUP> · K<SUP>-1</SUP> for the alloy ingot and ribbon, respectively. Using Landau's phase-transition theory, and careful analyses of the magnetic data around the FM-PM transition region, we have determined the critical parameters (T<SUB>C</SUB>, β, γ, and δ) in the low field range (below 10 kOe) with T<SUB>C</SUB> = 294.8 K, β = 0.469 ± 0.011, γ = 1.149 ± 0.060, and δ = 3.4 ± 0.1 for the alloy ingot, and with T<SUB>C</SUB> = 294.4 K, β = 0.449 ± 0.005, γ = 1.319 ± 0.040, and δ = 3.9 ± 0.1 for the alloy ribbon. One can see that β values fall in between those expected for the 3-D Heisenberg model (β = 0.365) and mean-field theory (β = 0.5). This indicates a coexistence of short-range and long-range FM interactions in both the samples. The nature of changes in value related to the critical parameters and maximum ΔS<SUB>m</SUB> is thoroughly discussed by means of structural analyses.</P>

      • Kinetics and modeling of hydrogen iodide decomposition for a bench-scale sulfur-iodine cycle

        Nguyen, T.D.B.,Gho, Y.K.,Cho, W.C.,Kang, K.S.,Jeong, S.U.,Kim, C.H.,Park, C.S.,Bae, K.K. Applied Science Publishers 2014 APPLIED ENERGY Vol.115 No.-

        In this work, the decomposition of hydrogen iodide (HI) over platinum catalyst in a frame work of the development of a bench-scale Sulfur-Iodine (S-I) cycle is studied. The catalyst Pt/γ-alumina 1.0wt% is prepared by impregnation-calcination method. The experiments of HI decomposition over the as-prepared catalyst are conducted at the temperature range of 350-550<SUP>o</SUP>C and at the atmospheric pressure. The experimental data are then used to estimate new kinetic parameters for HI decomposition on the basis of Langmuir-Hinshelwood type where the surface reaction is considered as the rate-limiting step. The kinetics with the estimated parameters shows a reasonable agreement with the experimental data. It also reflects the fact that, HI conversion is significantly decreased with a small amount of iodine present in the feeding solution. Thereafter, the kinetic model is applied to the modeling of a HI decomposer for the hydrogen production rate of 1Nm<SUP>3</SUP>/h in which hot helium gas is used to provide heat for the decomposition. Effects of heat-exchanger reactor configuration and composition of the feeding solution on the reactor size and the heat consumed are examined using the proposed model. Calculation results show that heat consumed for the co-current configuration is less than that for the counter-current configuration of the reactor. I<SUB>2</SUB> impurity and high water content in the feeding solution also result in an increase of reactor size and the heat required.

      • KCI등재

        Analyses of the Potential Capabilities and Factors Affecting Vietnamese Fruit Exports

        ( Nguyen¸ T. S. ),( B. H. Lee ) 강원대학교 농업생명과학연구원(구 농업과학연구소) 2020 강원 농업생명환경연구 Vol.32 No.S

        Trade data from 10 countries spanning 21 years was analyzed via revealed comparative advantage (RCA) index with gravity model adaptation (e.g., export equation by estimation methodology) to determine the export capabilities and the primary factors affecting Vietnamese fruit exportation. The data was obtained from the International Trade Center (ITC) database, Free Map Tools, and the United National Conference on Trade and Development (UNCTAD). The RCA index showed that Vietnam has a comparative advantage in exporting fruit (RCA > 1), specifically in coconut, Brazil nut, and cashew nut exports. The export equation result (least squares regression) indicated that factors could positively or negatively affect the quantity of exported fruits. The competitor’s export price, China’s participation, and the import country’s gross domestic product (GDP) per capita positively affected the quantity. The distance and the currency exchange rate between Vietnam and the importing country, the Vietnamese fruit export price, the agricultural area per capita, and the value of imported fruits to Vietnam negatively affected the quantity. Quantile regression analysis showed that Vietnamese fruit trading depends on the export scale. These results suggest an efficient strategy for developing the Vietnamese fruit industry, particularly in fruit exportation.

      • SCISCIESCOPUS

        T-RFLP reveals high &bgr;-Proteobacteria diversity in microbial fuel cells enriched with domestic wastewater

        Lefebvre, O.,Ha Nguyen, T.T.,Al-Mamun, A.,Chang, I.S.,Ng, H.Y. Blackwell Publishing Ltd 2010 Journal of applied microbiology Vol.109 No.3

        <P>Abstract</P><P>Aims: </P><P>To assess the biodiversity of a large number of microbial fuel cell (MFC) anodes from a variety of MFC designs, all enriched with domestic wastewater, using a molecular fingerprinting method.</P><P>Methods and Results: </P><P>We optimized a protocol allowing the rapid characterization of MFC communities using terminal restriction fragment length polymorphism (T-RFLP) with two different sets of primers and a varying number of restriction enzymes. This protocol was further validated by direct comparison with bacterial clone libraries. Twenty-one MFC anodes were analysed by T-RFLP. We also provided a statistical comparison with other bacterial communities from environments sharing common features.</P><P>Conclusions: </P><P>Bacterial communities were dominated by &bgr;-Proteobacteria, mostly belonging to the Burkholderiales order, that are known to play an active role in the cycle of metals such as iron and manganese. This property may allow them to properly pass electrons to the anode of an MFC.</P><P>Significance and Impact of the Study: </P><P>Unlike other groups, &bgr;-Proteobacteria have seldom been acknowledged as potentially efficient electrochemically active bacteria (EAB) in MFCs. Yet, they are plentiful in natural environments like biocorrosion biofilms and acid mine drainages that consequently show some potential for MFC enrichment.</P>

      • SCISCIESCOPUS

        Investigation of structural transition of dsDNA on various substrates studied by atomic force microscopy.

        Nguyen, T H,Kim, Y U,Kim, K J,Choi, S S American Scientific Publishers 2009 Journal of nanoscience and nanotechnology Vol.9 No.3

        <P>Structural transition of single dsDNA molecule which is immobilized on 3-aminopropyltriethoxysilane (APTES) treated substrate (APTES/substrate) or alkylthiol treated substrate (alkylthiol/substrate) has been investigated by atomic force microscopy (AFM). The obtained force versus distance (F-D) curves are used to dissect the transition from B-form to S-form, the melting from double stranded (ds) to single stranded (ss) DNA, and its Young's modulus as well as persistence length. The melt from dsDNA to ssDNA is evidenced by fitting with freely jointed chain (FJC) model. FJC fit and Young's modulus or persistence length values when the molecules are fixed on alkylthiol/substrate are more agreeable with other studies than those on APTES. We have clarified the different results of those experiments by analyzing the binding force between DNA molecules and APTES or alkylthiol linkers on the substrate. The DNA binding to APTES linker is much stronger than that on alkylthiol/substrate.</P>

      • Performance evaluation for dual circulating fluidized-bed steam gasifier of biomass using quasi-equilibrium three-stage gasification model

        Ngo, S.I.,Nguyen, T.D.B.,Lim, Y.I.,Song, B.H.,Lee, U.D.,Choi, Y.T.,Song, J.H. Applied Science Publishers 2011 APPLIED ENERGY Vol.88 No.12

        The effects of gasification temperature (T<SUB>G</SUB>) and steam to fuel ratio (γ) on product gas composition and yield were experimentally investigated for steam gasification of pine woodchips in a bench-scale circulating fluidized-bed (CFB) gasifier with external heat supplier. To evaluate process performance in a dual circulating fluidized-bed (DFB) with heat carrier (silica sand), a quasi-equilibrium three-stage gasification (qETG) model was developed and validated with experimental data of biomass steam gasification. The model was divided into three stages including biomass pyrolysis, char-gas reactions, and gas-phase reactions. Carbonic and methane formation ratios were considered at the pyrolysis stage under the assumption of spontaneous decomposition. At the second and third stages, char-gas and gas-phase equilibrium reactions were corrected by two empirical equations concerning the steam participation ratio and the non-equilibrium factor, respectively. Using the qETG model, parametric study on T<SUB>G</SUB> and γ was performed to predict final gas composition, carbon conversion, char residue, gas yield, lower heating value, additional fuel ratio, solid circulation ratio, heat recovery and H<SUB>2</SUB> to CO molar ratio. Focusing on the solid circulation ratio and H<SUB>2</SUB>/CO molar ratio, several effective operating conditions were suggested from the contour of performance criteria.

      • Coronary Atherosclerosis T<sub>1</sub>-Weighed Characterization With Integrated Anatomical Reference

        Xie, Y.,Kim, Y.J.,Pang, J.,Kim, J.S.,Yang, Q.,Wei, J.,Nguyen, C.T.,Deng, Z.,Choi, B.W.,Fan, Z.,Bairey Merz, C.N.,Shah, P.K.,Berman, D.S.,Chang, H.J.,Li, D. Elsevier Science B.V. Amsterdam 2017 JACC CARDIOVASCULAR IMAGING Vol.10 No.6

        Objectives: The aim of this work is the development of coronary atherosclerosis T<SUB>1</SUB>-weighted characterization with integrated anatomical reference (CATCH) technique and the validation by comparison with high-risk plaque features (HRPF) observed on intracoronary optical coherence tomography (OCT) and invasive coronary angiography. Background: T<SUB>1</SUB>-weighted cardiac magnetic resonance with or without contrast media has been used for characterizing coronary atherosclerosis showing promising prognostic value. Several limitations include: 1) coverage is limited to proximal coronary segments; 2) spatial resolution is low and often anisotropic; and 3) a separate magnetic resonance angiography acquisition is needed to localize lesions. Methods: CATCH acquired dark-blood T<SUB>1</SUB>-weighted images and bright-blood anatomical reference images in an interleaved fashion. Retrospective motion correction with 100% respiratory gating efficiency was achieved. Reference control subjects (n = 13) completed both pre- and post-contrast scans. Stable angina patients (n = 30) completed pre-contrast scans, among whom 26 eligible patients also completed post-contrast scans. After cardiac magnetic resonance, eligible patients (n = 22) underwent invasive coronary angiography and OCT for the interrogation of coronary atherosclerosis. OCT images were assessed and scored for HRPF (lipid-richness, macrophages, cholesterol crystals, and microvessels) by 2 experienced analysts blinded to magnetic resonance results. Results: Per-subject analysis showed none of the 13 reference control subjects had coronary hyperintensive plaques (CHIP) in either pre-contrast or post-contrast CATCH. Five patients had CHIP on pre-contrast CATCH and 5 patients had CHIP on post-contrast CATCH. Patients with CHIP had greater lipid abnormality than those without. Per-segment analysis showed elevated pre- and post-contrast plaque to myocardium signal ratio in the lesions with HRPF versus those without. Positive correlation was observed between plaque to myocardium signal ratio and OCT HRPF scoring. CHIP on pre-contrast CATCH were associated with significantly higher stenosis level than non-CHIP on invasive coronary angiography. Conclusions: CATCH provided accelerated whole heart coronary plaque characterization with simultaneously acquired anatomical reference. CHIP detected by CATCH showed positive association with high-risk plaque features on invasive imaging studies.

      • Second-Order Phase Transition and the Magnetocaloric Effect in <inline-formula> <tex-math notation='TeX'> <tex> ${\rm La}_{{0.7}}{\rm Ca}_{0.3-{x}}{\rm Sr}_{x}{\rm MnO}_{{3}}$ </tex> </tex-math></inline-formula> Nanoparticles

        Tran Dang Thanh,Phan, T. L.,Nguyen Van Chien,Do Hung Manh,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.4

        <P>In this paper, we present a detailed study of the magnetocaloric effect and critical properties around the ferromagnetic-paramagnetic (FM-PM) phase transition of La<SUB>0.7</SUB>Ca<SUB>0.3-x</SUB>Sr<SUB>x</SUB>MnO<SUB>3</SUB> nanoparticles with x = 0.10, 0.11, and 0.12. The samples were synthesized by a combination of reactive milling and thermal processing. The average crystallite size of nanoparticles estimated from the linewidth of X-ray diffraction peaks by using the Williamson-Hall method is about 50 nm. Under a magnetic field change of 10 kOe, the maximum magnetic entropy change (|ΔS<SUB>max</SUB>|) reaches values of 1.47, 1.42, and 1.38 J·kg<SUP>-1</SUP>·K<SUP>-1</SUP> for x = 0.10, 0.11, and 0.12, respectively, at around 300 K. The refrigerant capacity is thus in between 44 and 54 J·kg<SUP>-1</SUP>. Particularly, the M<SUP>2</SUP> versus H/M curves prove that all the samples exhibit a second-order magnetic phase transition. Based on Landau's phase-transition theory and careful analyses of the magnetic data around the FM-PM transition region, we have determined the critical exponents β, y, δ, and T<SUB>C</SUB>. Here, the β values obtained are 0.397, 0.453, and 0.456 for x = 0.10, 0.11, and 0.12, respectively, which are in between those expected on the basis of the mean-field theory (β = 0.5) and value of the 3-D Heisenberg model (β = 0.365). The result proves the coexistence of shortand long-range FM interactions in La<SUB>0.7</SUB>Ca<SUB>0.3-x</SUB>Sr<SUB>x</SUB>MnO<SUB>3</SUB> nanoparticles. The nature of this phenomenon is discussed thoroughly.</P>

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