Nonradiative energy transfer between colloidal quantum dot-phosphors and nanopillar nitride LEDs.

Zhang, Fan,Liu, Jie,You, Guanjun,Zhang, Chunfeng,Mohney, Suzanne E,Park, Min Joo,Kwak, Joon Seop,Wang, Yongqiang,Koleske, Daniel D,Xu, Jian Optical Society of America 2012 Optics express Vol.20 No.2

<P>We present in this communication our study of the nonradiative energy transfer between colloidal quantum dot (QD) phosphors and nitride nanopillar light emitting diodes (LEDs). An epitaxial p-i-n InGaN/GaN multiple quantum-well (QW) heterostructure was patterned and dry-etched to form dense arrays of nanopillars using a novel etch mask consisting of self-assembled In3Sn clusters. Colloidal QD phosphors have been deposited into the gaps between the nanopillars, leading to sidewall coupling between the QDs and InGaN QW emitters. In this approach, close QW-QD contact and a low-resistance design of the LED contact layer were achieved simultaneously. Strong non-radiative energy transfer was observed from the InGaN QW to the colloidal QD phosphors, which led to a 263% enhancement in effective internal quantum efficiency for the QDs incorporated in the nanopillar LEDs, as compared to those deposited over planar LED structures. Time-resolved photoluminescence was used to characterize the energy transfer process between the QW and QDs. The measured rate of non-radiative QD-QW energy-transfer agrees well with the value calculated from the quantum efficiency data for the QDs in the nanopillar LED.</P>

On Performability Assessment of Communication Networks under Dependent Link Failure

Zhang Fan,Youheng Liu 한국통신학회 1993 Asia-Pacific Conference on Communications Vol.2 No.1

Structural Characterization and Optical Properties of Sol-gel-derived Polycrystalline Pb(Zr0.35Ti0.65)O3 Thin Films

Fan Zhang,Rong-Jun Zhang,Zi YiWang,Yu-Xiang Zheng,Song-You Wang,Hai-Bin Zhao,Liang-Yao Chen,Xiao Bin Liu,An Quan Jiang 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.1

Polycrystalline Pb(Zr0.35Ti0.65)O3 thin films prepared on Pt/Ti/SiO2/Si substrate by using solgel technique were characterized by using X-ray diffraction (XRD) and atomic force microscopy (AFM). The optical properties of the films were investigated by using spectroscopic ellipsometry (SE) with a four-phase optical model, air/roughness layer/PZT layer/Pt layer in the spectral range of 300 - 800 nm. The optical band gap of the films calculated following the Tauc’s Law was smaller than that of an amorphous PZT thin film with some microcrystals existing on the surface. The result indicates that the quantum-size effect leads to an increase in band gap when the crystalline dimensions become very small.

Eccentrically compressive behaviour of RC square short columns reinforced with a new composite method

Fan Zhang,Yi-Yan Lu,Shan Li,Wenlong Zhang 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.1

A new composite reinforced method, namely self-compacting concrete filled circular CFRP-steel jacketing, was proposed in this paper. Experimental tests on eight RC square short columns reinforced with the new composite reinforced method and four RC square short columns reinforced with CFS jackets were conducted to investigate their eccentrically compressive behaviour. Nine reinforced columns were subjected to eccentrically compressive loading, while three reinforced columns were subjected to axial compressive loading as reference. The parameters investigated herein were the eccentricity of the compressive loading and the layer of CFRP. Subsequently, the failure mode, ultimate load, deformation and strain of these reinforced columns were discussed. Their failure modes included the excessive bending deformation, serious buckling of steel jackets, crush of concrete and fracture of CFRP. Moreover, these reinforced columns exhibited a ductile failure globally. Both the eccentricity of the compressive loading and the layer of CFRP had a significant effect on the eccentrically compressive behaviour of reinforced columns. Finally, formulae for the evaluation of the ultimate load of reinforced columns were proposed. The theoretical formulae based on the ultimate equilibrium theory provided an effective, acceptable and safe method for designers to calculate the ultimate load of reinforced columns under eccentrically compressive loading.

Active Gate Charge Control Strategy for Series-Connected IGBTs

Fan Zhang,Yu Ren,Mofan Tian,Xu Yang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Since the voltage blocking capability of a single insulated gate bipolar transistor (IGBT) is limited, series-connected IGBTs are used in power electronic converters to satisfy the requirements of high-power and high-voltage applications. However, due to the parameter differences of the series-connected IGBTs, it is difficult to ensure an equal voltage sharing between the devices during both transient and steady-state operations. This paper proposes a novel active gate drive which operates basing on the active gate charge control strategy. The proposed active gate drive is able to achieve both minimized power loss and proper voltage sharing between the series-connected IGBTs. The active gate charge control strategy has been validated by simulations, and promising results have been obtained.

Research on Participation and Position Evaluation of Korean Manufacturing Global Value Chain: Based on the Comparative Analysis with China and the United States

Fan Zhang,Shuai Su 한국무역학회 2021 Journal of Korea trade Vol.25 No.2

Purpose – This article will take the Korean manufacturing industry as an example to estimate Korea’s global value chain status from the perspective of overall and sub-industry, hoping to provide a theoretical reference for Korean manufacturing to climb the global value chain. Design/methodology – Based on the WIOD data. The data is calculated by using MATLAB (2014a) coding. The data for 6 sectors are classified according to the International Standard Industrial Classification revision 3 (ISIC Rev. 3), the WIOD data are used to calculate and compare the position, participation and dynamics of the Korea, China and USA` manufacturing industry in the 1995-2016. Findings – The empirical results supported conclusions of the theoretical model. In the Korean GVC of electrical and optical sector, while stronger forward linkages than backward linkages to GVC are advantageous for an average advanced country, the benefits of downstream tasks are pronounced for non-advanced countries. And proved the correlation for an index to capture a country’s upstream position or downstream position, it makes sense to compare that Korea’s exports of intermediates in the same sector that are used by China and USA. Originality/value – The first is to re-examine the characteristics of South Korea’s participation in global value chains under a more systematic and accurate theoretical framework, which provides a new empirical reference for related research; the second is to content covers of the manufacturing 6 sectors, so as to more completely describe the characteristics of Korean manufacturing’s participation in global value chains; The value of this paper is providing empirical evidence of the effect of Korea’s the GVC of manufacturing sectors. In the GVC of 6 sectors, first three have a higher position in the value chain and are in the upper middle and upper reaches of the GVC. The latter two have a low GVC position index, which has become the main sector that pulls down the overall position of Korea’s manufacturing industry.

2D and 3D numerical analysis on strut responses due to one-strut failure

Zhang, Wengang,Zhang, Runhong,Fu, Yinrong,Goh, A.T.C.,Zhang, Fan Techno-Press 2018 Geomechanics & engineering Vol.15 No.4

In deep braced excavations, struts and walers play an essential role in the whole supporting system. For multi-level strut systems, accidental strut failure is possible. Once a single strut fails, it is possible for the loads carried from the previous failed strut to be transferred to the adjacent struts and therefore cause one or more struts to fail. Consequently, progressive collapse may occur and cause the whole excavation system to fail. One of the reasons for the Nicoll Highway Collapse was attributed to the failure of the struts and walers. Consequently, for the design of braced excavation systems in Singapore, one of the requirements by the building authorities is to perform one-strut failure analyses, in order to ensure that there is no progressive collapse when one strut was damaged due to a construction accident. Therefore, plane strain 2D and three-dimensional (3D) finite element analyses of one-strut failure of the braced excavation system were carried out in this study to investigate the effects of one-strut failure on the adjacent struts.

Infestation and Related Ecology of Chigger Mites on the Asian House Rat (Rattus tanezumi) in Yunnan Province, Southwest China

Fan Ding,Wen-Li Jiang,Xian-Guo Guo,Rong Fan,Cheng-Fu Zhao,Zhi-Wei Zhang,Ke-Yu Mao,Rong Xiang 대한기생충학열대의학회 2021 The Korean Journal of Parasitology Vol.59 No.4

Analysis of Factors Impacting Atmospheric Pressure Plasma Polishing

Zhang, Ju-Fan,Wang, Bo,Dong, Shen Korean Society for Precision Engineering 2008 International Journal of Precision Engineering and Vol.9 No.2

Atmospheric pressure plasma polishing (APPP) is a noncontact precision machining technology that uses low temperature plasma chemical reactions to perform atom-scale material removal. APPP is a complicated process, which is affected by many factors. Through a preliminary theoretical analysis and simulation, we confirmed that some of the key factors are the radio frequency (RF) power, the working distance, and the gas ratio. We studied the influence of the RF power and gas ratio on the removal rate using atomic emission spectroscopy, and determined the removal profiles in actual operation using a commercial form talysurf. The experimental results agreed closely with the theoretical simulations and confirmed the effect of the working distance. Finally, we determined the element compositions of the machined surfaces under different gas ratios using X-ray photoelectron spectroscopy to study the influence of the gas ratio in more detail. We achieved a surface roughness of Ra 0.6 nm on silicon wafers with a peak removal rate of approximately 32 $mm^{3}$/min.

Effect of Indium Concentration on the Morphological and Photoluminescence Properties of In-doped ZnO Nanorods

Fan ZHANG,김홍승,장낙원 한국물리학회 2017 New Physics: Sae Mulli Vol.67 No.11

In-doped ZnO nanorods with various indium concentrations were grown on silicon substrates with a ZnO seed layer by using the hydrothermal method. Although well-aligned undoped ZnO nanorods were synthesized and crystallized in a hexagonal structure with good quality, once an indium source had been introduced, the diameter of the In-doped ZnO nanorod showed a linear increase with one exception: a decrease in the diameter of the In-doped ZnO nanorod with 5 wt.% indium. Correspondingly, the crystalline quality and the optical properties of In-doped ZnO nanorods improved with increasing indium concentration. In conclusion, the indium-doping concentration plays an important role in determining morphology and the photoluminescence properties of In-doped ZnO nanorods. The possible growth mechanism, which is affected by the indium doping at different concentration, is discussed.