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Kumar, N. (author), Strikwerda, A.C. (author), Fan, K. (author), Zhang, X. (author), Averitt, R.D. (author), Planken, P.C.M. (author), Adam, A.J.L. (author)We report on direct measurements of the magnetic near-field of metamaterial split ring resonators at terahertz frequencies using a magnetic field sensitive material. Specifically, planar split ring resonators are fabricated on a single magneto-optically active terbium gallium garnet crystal. Normally incident terahertz radiation couples to the...journal article 2012
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Poelma, R.H. (author), Morana, B. (author), Vollebregt, S. (author), Schlangen, H.E.J.G. (author), Van Zeijl, H.W. (author), Fan, X. (author), Zhang, G.Q. (author)The porous nature of carbon nanotube (CNT) arrays allows for the unique opportunity to tailor their mechanical response by the infiltration and deposition of nanoscale conformal coatings. Here, we fabricate novel photo-lithographically defined CNT pillars that are conformally coated with amorphous silicon carbide (a-SiC) to strengthen the...journal article 2014
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Chen, Xianping (author), Ye, H. (author), Fan, Xuejun (author), Ren, Tianling (author), Zhang, Kouchi (author)Heat pipes (HPs) have received considerable attention in recent decades, especially in the field of cooling electronics, which requires the removal of added heat from an area of limited volume to the environment. Small HPs are widely used in electronic applications, which are normally limited by the compact structure and dimensions of the...journal article 2016
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Ye, H. (author), Leung, Stanley Y.Y. (author), Wong, K.Y. (author), Chen, Xianping (author), Lin, Kai (author), Fan, J. (author), Kjelstrup, Signe (author), Fan, Xuejun (author), Zhang, Kouchi (author)Using the analogue of the electric inductance, we reveal the properties of the thermal inductance in GaN-based light-emitting diode devices by testing their transient thermal behaviors. We find that the devices exhibit a transient thermal response under step-down or step-up currents and observe notable inductive phenomena of the temperature...journal article 2016
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Fan, Jiajie (author), Mohamed, Moumouni Guero (author), Qian, Cheng (author), Fan, Xuejun (author), Zhang, Kouchi (author), Pecht, Micheal (author)With the expanding application of light-emitting diodes (LEDs), the color quality of white LEDs has attracted much attention in several color-sensitive application fields, such as museum lighting, healthcare lighting and displays. Reliability concerns for white LEDs are changing from the luminous efficiency to color quality. However, most of the...journal article 2017
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Qian, Cheng (author), Fan, Jiajie (author), Fang, Jiayi (author), Yu, Chaohua (author), Ren, Y. (author), Fan, Xuejun (author), Zhang, Kouchi (author)By solving the problem of very long test time on reliability qualification for Light-emitting Diode (LED) products, the accelerated degradation test with a thermal overstress at a proper range is regarded as a promising and effective approach. For a comprehensive survey of the application of step-stress accelerated degradation test (SSADT) in...journal article 2017
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Qian, Cheng (author), Fan, Jiajie (author), Fan, Xuejun (author), Zhang, Kouchi (author)The spectral power distribution (SPD) is considered as the figureprint of a light emitting diode (LED). Based on the analysis on its SPD, a method to predict both lumen depreciation and color shift for the phosphor converted white LEDs (pc-LEDs) is proposed in this paper. First, the entire SPD of a pc-LED is predicted by superimposing two...journal article 2017
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Sun, B. (author), Fan, Xuejun (author), Li, Lei (author), Ye, H. (author), van Driel, W.D. (author), Zhang, Kouchi (author)This paper studies the interaction of catastrophic failure of the driver and LED luminous flux decay for an integrated LED lamp with an electrolytic capacitor-free LED driver. Electronic thermal simulations are utilized to obtain the lamp's dynamic history of temperature and current for two distinct operation modes: constant current mode (CCM...journal article 2017
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Sun, B. (author), Fan, Xuejun (author), Fan, J. (author), Zhang, Kouchi (author), Qian, Cheng (author)In this work, a physics-of-failure (PoF) reliability prediction methodology is combined with statistical models to consider the interaction between the lumen depreciation and catastrophic failures of LEDs. The current in each LED may redistribute when the catastrophic failure occurs in one of LEDs in an array, thus affecting the operation...conference paper 2017
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Tang, H. (author), Ye, H. (author), Wong, K.Y. (author), Leung, Stanley Y.Y. (author), Fan, Jiajie (author), Chen, Xianping (author), Fan, Xuejun (author), Zhang, Kouchi (author)The objective of this study is to quantitatively evaluate the impacts of LED components on the overdriving reliability of high power white LED chip scale packages (CSPs). The reliability tests under room temperature are conducted over 1000 h in this study on CSP LEDs with overdriving currents. A novel method is proposed to investigate the...journal article 2017
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Chen, Liangbiao (author), Zhou, Jiang (author), Chu, Hsing-wei (author), Zhang, Kouchi (author), Fan, Xuejun (author)While moisture diffusion in microelectronic device and packaging has been studied for decades, the problems involving complex nonlinear moisture diffusion in multi-material assembly have not been fully studied. This paper has developed a general nonlinear diffusion model by adopting water activity, a continuous state variable, as the field...journal article 2017
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Sun, B. (author), Fan, Xuejun (author), Ye, H. (author), Fan, Jiajie (author), Qian, Cheng (author), van Driel, W.D. (author), Zhang, Kouchi (author)In this paper, an integrated LED lamp with an electrolytic capacitor-free driver is considered to study the coupling effects of both LED and driver's degradations on lamp's lifetime. An electrolytic capacitor-less buck-boost driver is used. The physics of failure (PoF) based electronic thermal simulation is carried out to simulate the lamp's...journal article 2017
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Tang, H. (author), Ye, Huai-Yu (author), Chen, Xian-Ping (author), Qian, Cheng (author), Fan, Xue-Jun (author), Zhang, Kouchi (author)In this paper, the heat transfer performance of the multi-chip (MC) LED module is investigated numerically by using a general analytical solution. The configuration of the module is optimized with genetic algorithm (GA) combined with a response surface methodology. The space between chips, the thickness of the metal core printed circuit board...journal article 2017
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Yang, Ning (author), Yang, Daoguo (author), Zhang, Kouchi (author), Chen, Liangbiao (author), Liu, Dongjing (author), Cai, Miao (author), Fan, Xuejun (author)The effects of graphene stacking are investigated by comparing the results of methane adsorption energy, electronic performance, and the doping feasibility of five dopants (i.e., B, N, Al, Si, and P) via first-principles theory. Both zigzag and armchair graphenes are considered. It is found that the zigzag graphene with Bernal stacking has...journal article 2018
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Liu, Yang (author), Zhang, H. (author), Wang, Lingen (author), Fan, Xuejun (author), Zhang, Kouchi (author), Sun, Fenglian (author)The microstructure, thickness, porosity, and shear performance of the silver (Ag) sintering layers under different sintering pressures were investigated. Experimental results demonstrated that the thickness and the porosity of the sintering layer decreased when the sintering pressure varied from 5 MPa to 30 MPa. This densification phenomenon...journal article 2018
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Zhang, H. (author), Liu, Yang (author), Wang, Lingen (author), Fan, Jiajie (author), Fan, Xuejun (author), Sun, Fenglian (author), Zhang, Kouchi (author)High reliable packaging materials are needed for electronics when they work at harsh environments. Among which, the nanosilver material has been widely studied and applied in power electronics due to its low processing temperature and high reliability. This paper investigates the bonding properties of nanosilver sintered hermetic cavity. There...journal article 2018
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Sun, Bo (author), Fan, Xuejun (author), van Driel, W.D. (author), Cui, Chengqiang (author), Zhang, Kouchi (author)In this study, we present a general methodology that combines the reliability theory with physics of failure for reliability prediction of an LED driver. More specifically, an integrated LED lamp, which includes an LED light source with statistical distribution of luminous flux, and a driver with a few critical components, is considered. The...journal article 2018
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Qian, C. (author), Mirza Gheytaghi, Amir (author), Fan, J. (author), Tang, H. (author), Sun, B. (author), Ye, H. (author), Zhang, Kouchi (author)As an increasing attention towards sustainable development of energy and environment, the power electronics (PEs) are gaining more and more attraction on various energy systems. The insulated gate bipolar transistor (IGBT), as one of the PEs with numerous advantages and potentials for development of higher voltage and current ratings, has been...journal article 2018
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Cui, Z. (author), Chen, Xianping (author), Fan, Xuejun (author), Zhang, Kouchi (author)Interfacial properties of Cu/SiO2 in semiconductor devices has continued to be the subject of challenging study for many years because of its difficulties in experimentally quantifying the critical strength of interface. In this paper, a multi-scale modeling approach is built to characterize the interfacial properties between Cu and SiO2. In...conference paper 2018
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Sun, B. (author), Fan, J. (author), Fan, Xuejun (author), Zhang, Kouchi (author)This work studies the effect of randomness of LED's lumen depreciation on reliability of the entire LED lamp. An integrated LED light bulb is selected as carrier of the proposed method. A PoF based lumen depreciation model and electronic-thermal simulations are introduced for reliability prediction. The normal distribution is used to describe...conference paper 2018