Influence of Crystallite Size on Magnetocaloric Effect and Critical Behavior La_0.7Sr_0.3Mn_0.92Co_0.08O₃ Nanoparticles

Tran Dang Thanh,Dinh Chi Linh,Le Viet Bau,Thi Anh Ho,Tien Van Manh,The-Long Phan,Seong-Cho Yu IEEE 2015 IEEE transactions on magnetics Vol.51 No.1

<P>Four samples of La<SUB>0.7</SUB>Sr<SUB>0.3</SUB>Mn<SUB>0.92</SUB>Co<SUB>0.08</SUB>O<SUB>3</SUB> (LSMCO) with different crystallite sizes were prepared by the combination of solid-state reaction and mechanical milling methods. Based on isothermal magnetization data, M(H), temperature dependences of magnetic entropy change, ΔS<SUB>m</SUB>T, of the samples under a magnetic field change of 10 kOe were calculated. The maximum values of magnetic entropy change (|ΔS<SUB>max</SUB>|) at room temperature are in the range of 0.9-1.4 J · kg<SUP>-1</SUP> · K<SUP>-1</SUP>, corresponding to ferromagnetic (FM)-paramagnetic phase transition. In addition, M<SUP>2</SUP> versus H/M curves at temperatures around TC prove the samples exhibiting a second-order magnetic phase transition. The critical exponents β, γ, and δ were determined using the modified Arrott plot method and critical isotherm analysis. Here, these exponent values are located in between those expected for the mean-field theory and 3-D Heisenberg model. It means the coexistence of short-range and long-range FM interactions in LSMCO nanoparticles.</P>

Coexistence of short- and long-range ferromagnetic order in La_0.7Sr_0.3Mn_1−xCo_xO₃ compounds

Thanh, Tran Dang,Linh, Dinh Chi,Manh, T. V.,Ho, T. A.,Phan, The-Long,Yu, S. C. American Institute of Physics 2015 Journal of Applied Physics Vol.117 No.17

Effects of π-conjugation on the charge-transport properties of hole-transporting materials featuring diphenylamine- π-quinacridone for perovskite solar cells: A theoretical study

Rashid Md Al Mamunur,Kim Junkyu,Long Dang Xuan,Kwak Kyungwon,Hong Jongin 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.5

Density functional theory (DFT), time-dependent DFT, and Marcus theory were used to probe the optoelectronic and charge-transport properties of compounds obtained by inserting long-chain aliphatic alkenes or condensed aromatic rings between the planar quinacridone core and the terminal donor diphenylamine moiety of a reference hole-transporting material (HTM). Compared to the reference HTM, its newly designed derivatives showed lower-lying highest occupied molecular orbitals that were well matched in energy with the valence band maximum of a representative perovskite absorber. HTMs obtained via the insertion of condensed aromatic rings showed higher hole mobilities than those obtained via the insertion of aliphatic alkenes. Overall, hole mobility was mainly influenced by the charge-transfer integral, while other factors, such as the hole reorganization energy, hole hopping rate, and centroid distance, had only minor effects.

Controlling charge injection properties in polymer field-effect transistors by incorporation of solution processed molybdenum trioxide

Long, Dang Xuan,Xu, Yong,Wei, Huai-xin,Liu, Chuan,Noh, Yong-Young The Royal Society of Chemistry 2015 Physical chemistry chemical physics Vol.17 No.31

<P>A simply and facilely synthesized MoO<SUB>3</SUB> solution was developed to fabricate charge injection layers for improving the charge-injection properties in p-type organic field-effect transistors (OFETs). By dissolving MoO<SUB>3</SUB> powder in ammonium (NH<SUB>3</SUB>) solvent under an air atmosphere, an intermediate ammonium molybdate ((NH<SUB>4</SUB>)<SUB>2</SUB>MoO<SUB>4</SUB>) precursor is made stable, transparent and spin-coated to form the MoO<SUB>3</SUB> interfacial layers, the thickness and morphology of which can be well-controlled. When the MoO<SUB>3</SUB> layer was applied to OFETs with a cost-effective molybdenum (Mo) electrode, the field-effect mobility (<I>μ</I><SUB>FET</SUB>) was significantly improved to 0.17 or 1.85 cm<SUP>2</SUP> V<SUP>−1</SUP>s<SUP>−1</SUP> for polymer semiconductors, regioregular poly(3-hexylthiophene) (P3HT) or 3,6-bis-(5bromo-thiophen-2-yl)-<I>N</I>,<I>N</I>′-bis(2-octyl-1-dodecyl)-1,4-dioxo-pyrrolo[3,4-<I>c</I>]pyrrole (DPPT-TT), respectively. Device analysis indicates that the MoO<SUB>3</SUB>-deposited Mo contact exhibits a contact resistance <I>R</I><SUB>C</SUB> of 1.2 MΩ cm comparable to that in a device with the noble Au electrode. Kelvin-probe measurements show that the work function of the Mo electrode did not exhibit a dependence on the thickness of MoO<SUB>3</SUB> film. Instead, ultraviolet photoemission spectroscopy results show that a doping effect is probably induced by casting the MoO<SUB>3</SUB> layer on the P3HT semiconductor, which leads to the improved hole injection.</P> <P>Graphic Abstract</P><P>A simply synthesized MoO<SUB>3</SUB> is used as charge injection layers for printed p-type organic field-effect transistors (OFETs). <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5cp03369a'> </P>

Design Optimization of Photonic Crystal Structure for Improved Light Extraction of GaN LED

Dang Hoang Long,In-Kag Hwang,Sang-Wan Ryu IEEE 2009 IEEE journal of selected topics in quantum electro Vol.15 No.4

<P>We performed a theoretical analysis on improved light extraction efficiency of LEDs with photonic crystals (PCs). The light propagation and extraction of PC LEDs were simulated using the finite-difference time-domain method for various PC LED structures. LEDs with both top and bottom PCs and PC LEDs grown on patterned substrates were considered to maximize light extraction efficiency. The design parameters of the PC were varied, and optimized values were obtained. A disordered PC was simulated, and we showed that the light extraction efficiency of a disordered PC was nearly equivalent to that of an ordered PC with the same pattern periodicity. This result revealed that the increased light extraction of PC LEDs was mainly due to scattering. Moreover, by comparing the enhancement of PC LEDs with different shapes of air holes, we showed that only the density of holes and the area occupied by holes play important roles in light extraction. The shapes of the holes have no strong effect on the enhancement of light extraction.</P>

OSI-027 alleviates rapamycin insensitivity by modulation of mTORC2/AKT/TGF-β1 and mTORC1/4E-BP1 signaling in hyperoxia-induced lung injury infant rats

Long Li,Liang Mulin,Yanling Liu,Wang Pan,Dang Hongxing 대한독성 유전단백체 학회 2021 Molecular & cellular toxicology Vol.17 No.3

Background The mechanism of long time and high-concentration oxygen treatment leading to acute lung injury (ALI) or developmental lung disease in infants is currently unclear. Here we found that compared with the effect of rapamycin, pan-mTOR1/2 inhibitor OSI-027, alleviates hyperoxia-induced lung injury (HILI) by modulation of mTORC2/AKT/TGF-β1 and mTORC1/4E-BP1 signaling in infant rats. Objective Infant rats were treated with continuous inhalation of 90% medical oxygen. Normal saline, rapamycin, or OSI-027 was intraperitoneally injected, and the status of lung injury was tested on days 3, 7, and 14. The activation of mTOR/AKT/TGFβ1 and mTORC1/4E-BP1 signaling was confirmed by immunohistochemistry and Western blot analysis in normal and hyperoxia-treated live precision-cut lung tissues. The inhibitory effect of OSI-027 extended to the active state of other proteins implicated in mTOR1/2 signaling was demonstrated in hyperoxia-induced injured lung tissues. Results Our data demonstrate that hyperoxia-induced serious lung inflammation and fibrosis. OSI-027 significantly attenuated the pathological process of HILI, inhibit the phosphorylation of the primary downstream targets of mTORC1/C2, and reduce the activation of TGF-β1 signaling. Conclusions The results suggest that mTORC2/AKT/TGF-β1 and the rapamycin-insensitive mTORC1/4E-BP1 (Thr37/46) signaling has an important effect during HILI with a potential meaning for the progress of novel anti-hyperoxia-injury strategies. Background The mechanism of long time and high-concentration oxygen treatment leading to acute lung injury (ALI) or developmental lung disease in infants is currently unclear. Here we found that compared with the effect of rapamycin, pan-mTOR1/2 inhibitor OSI-027, alleviates hyperoxia-induced lung injury (HILI) by modulation of mTORC2/AKT/TGF-β1 and mTORC1/4E-BP1 signaling in infant rats. Objective Infant rats were treated with continuous inhalation of 90% medical oxygen. Normal saline, rapamycin, or OSI-027 was intraperitoneally injected, and the status of lung injury was tested on days 3, 7, and 14. The activation of mTOR/AKT/TGFβ1 and mTORC1/4E-BP1 signaling was confirmed by immunohistochemistry and Western blot analysis in normal and hyperoxia-treated live precision-cut lung tissues. The inhibitory effect of OSI-027 extended to the active state of other proteins implicated in mTOR1/2 signaling was demonstrated in hyperoxia-induced injured lung tissues. Results Our data demonstrate that hyperoxia-induced serious lung inflammation and fibrosis. OSI-027 significantly attenuated the pathological process of HILI, inhibit the phosphorylation of the primary downstream targets of mTORC1/C2, and reduce the activation of TGF-β1 signaling. Conclusions The results suggest that mTORC2/AKT/TGF-β1 and the rapamycin-insensitive mTORC1/4E-BP1 (Thr37/46) signaling has an important effect during HILI with a potential meaning for the progress of novel anti-hyperoxia-injury strategies.

Theoretical Analysis of the Light Extraction Efficiency of a Light-emitting Diode with a Bottom Photonic Crystal

Dang Hoang Long,In-Kag Hwang,Sang-Wan Ryu 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1

A light-emitting diode (LED) with a bottom photonic crystal (PC), where the PC was fabricated below the active layer, was theoretically analyzed to obtain its light extraction efficiency. A finitedifference time-domain (FDTD) method was used for the simulation of LEDs with top and bottom PCs, and their light extraction efficiencies were compared. The bottom PC was shown to be effective in increasing the extraction efficiency for a small distance from the PC to the active layer. This superior extraction efficiency was attributed to the large confinement of light between the top surface of the LED and the PC. For the analyzed designs, we theoretically estimated the enhancement of light extraction for various lattice constants, PC thicknesses, ratios of the hole radius to the lattice constant, and distances from the PC to the active layer. The optimized parameters were obtained for the highest light extraction efficiency. A light-emitting diode (LED) with a bottom photonic crystal (PC), where the PC was fabricated below the active layer, was theoretically analyzed to obtain its light extraction efficiency. A finitedifference time-domain (FDTD) method was used for the simulation of LEDs with top and bottom PCs, and their light extraction efficiencies were compared. The bottom PC was shown to be effective in increasing the extraction efficiency for a small distance from the PC to the active layer. This superior extraction efficiency was attributed to the large confinement of light between the top surface of the LED and the PC. For the analyzed designs, we theoretically estimated the enhancement of light extraction for various lattice constants, PC thicknesses, ratios of the hole radius to the lattice constant, and distances from the PC to the active layer. The optimized parameters were obtained for the highest light extraction efficiency.

Manganese Oxide Nanoparticle as a New p-Type Dopant for High-Performance Polymer Field-Effect Transistors

Long, Dang Xuan,Choi, Eun-Young,Noh, Yong-Young American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.29

<P>We report a new p-type dopant, manganese oxide (Mn3O4) nanoparticle, to enhance the performance of organic field-effect transistors (OFETs) with conjugated polymers, including poly(3-hexylthiophene-2,5-diyl), poly[[N,N 9-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)], and poly[[2,5-bis(2-octyldodecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl]-alt-[[2,2'-(2,5-thiophene)bis-thieno(3,2b) thiophene]-5,5'-diyl]] (DPPT-TT). Incorporating a small amount of Mn3O4 nanoparticles in the semiconductor film significantly improved the hole mobility and decreased the threshold voltage for all OFETs, indicating efficient Mn3O4 nanoparticle p-type doping. The Mn3O4 nanoparticle showed a better doping efficiency than the widely used FeCl3 dopant due to better mixability with the host conjugated polymers. In particular, doped DPPT-TT OFETs showed significantly improved mobility up to 2.35 (+/- 0.4) cm(2)/(V.s) with enhanced air and operational stability at 0.1 wt % doping concentration from 1.2 cm(2)/(V.s) for pristine devices.</P>

Analysis and Diagnosis Scheme of Parallel Arc Failure in DC Power Lines

Dang Hoang-Long,Kim Jae-Chang,Kwak Sangshin,Choi Seungdeog 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3

The arc phenomena usually relate to the undesired ejection of two electric conductors. The emission power discharge from an arc event might wrath the electrical lines and cause a fire. Numerous studies were proposed to detect arc events and isolate them in time. The DC arc faults are sorted into two common types: series and parallel arcs. Due to corrupting contamination or insulation, a parallel arc occurs between two electrical wiring. The parallel arc currents of the system can be considerably amplified compared with the series type. In this research, the characteristic behaviors of the system in both time and frequency domains are studied during DC parallel arc failures, and arc energy was also discussed and analyzed. The unique behaviors are adopted to identify parallel arcs in different conditions. Sorting electrical arcs that are beneficial and trustworthy for the judicial procedure and deciding the protection schemes. The analyzed process is based on different domains of load current, source current, and arc voltage.

Evaluation of Single-Phase DC–AC Converters with Condition Monitoring Algorithm of Aluminum Electrolytic Capacitors Using Artificial Learnings with Various Circuit Signals and Filtering Combinations

Dang Hoang-Long,Park Hye-Jin,Kwak Sangshin,Choi Seungdeog 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4

Capacitors are essential parts of power converters since the cost, size, and performance of converters are mainly dependent on them. Nevertheless, the capacitor is the most degeneration device among all converter parts owing to its aging failures and little lifetime. Thus, the monitoring process is an essential route for valuing health status and gives predictive maintenance to ensure steadiness in electric converter. The equivalent series resistance and the capacitance are commonly indexes employed for estimating the condition grade of capacitors. In this research, six artificial intelligence (AI) algorithms are adopted to estimate the aluminum capacitor (Al-Cap) parameters in the single-phase inverter system. Various circuit signals, such as load voltage and current, capacitor voltage and current, are examined by utilizing the discrete wavelet transform (DWT) analysis and the combinations of fast Fourier transform with various filters. The considered signals are handled as AI model’s inputs to guesstimate the health status of the Al-cap. In addition, the root-mean-square value is employed as an index to compare the accuracy with the analyzed signals. Furthermore, several indicators are mixed to acquire the best recipes for capacitor health evaluation.