Highly transparent Nd-doped yttria ceramics fabricated by hot pressing with ZrO₂ and La₂O₃ as sintering additives

Gan, Lin,Park, Young-Jo,Zhu, Lin-Lin,Kim, Ha-Neul,Ko, Jae-Woong,Lee, Jae-Wook Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.763 No.-

<P><B>Abstract</B></P> <P>Highly transparent Nd-doped yttria ceramics were fabricated by hot-pressing at 1600 °C with single addition and co-addition of ZrO<SUB>2</SUB> and La<SUB>2</SUB>O<SUB>3</SUB>. The binary additives were found to promote the densification of yttria more effectively than single addition, resulting in higher transmittance. The highest transmittance was obtained in the sample with 1 at.% ZrO<SUB>2</SUB> and 3 at.% La<SUB>2</SUB>O<SUB>3</SUB>, which reached 74.3% transparency at a wave length of 400 nm and 81.3% at 1100 nm. The optical absorption, luminescence, and fluorescence decay of this sample was investigated. The absorption cross-sections of the sample at 806 nm and 820 nm were 1.22 × 10<SUP>−20</SUP> and 1.31 × 10<SUP>−20</SUP> cm<SUP>2</SUP>, respectively. The strongest emission was measured at 1078 nm with a full-width at half-maximum of 5 nm with excitation at 808 nm and a fluorescence lifetime of 423 μs. Additionally, the microhardness of the all samples is ranging from 7.88 to 7.05 GPa with variation of the grain size from 0.85 to 1.81 μm, while the fracture toughness of the all samples is about 1 MPa m<SUP>1/2</SUP> and was found to be almost unchanged. These results have demonstrated that Nd-doped yttria ceramics for the application of laser gain media can be fabricated by hot-pressing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly transparent Nd-doped yttria ceramics fabricated by hot-pressing. </LI> <LI> Effects of ZrO<SUB>2</SUB>-La<SUB>2</SUB>O<SUB>3</SUB> additives on the samples were studied. </LI> <LI> The optical and mechanical properties of the samples were studied. </LI> </UL> </P>

Enhancement of the optical transmittance of hot-pressed transparent yttria ceramics by a multi-step sintering process

Gan, Lin,Park, Young-Jo,Zhu, Lin-Lin,Go, Shin-Il,Kim, Haneul,Kim, Jin-Myung,Ko, Jae-Woong Elsevier 2016 CERAMICS INTERNATIONAL Vol.42 No.12

<P><B>Abstract</B></P> <P>In this work, we report the enhancement of the optical transmittance of yttria ceramics via a ‘pre-sintering/hot-pressing/hot-isostatic pressing’ multi-step process. The in-line transmittance reaches 78.0% at 400nm and 83.2% at 1100nm with an average grain size of approximately 1µm. This sintering route is derived and upgraded from our previously reported one-step hot-pressing method for the fabrication of transparent yttria ceramics. Through the enhanced strength of the green body by pre-sintering, the formation of cracks and the breaking up of the as-hot-pressed samples can be effectively suppressed, leading to sound or crack-free but less transparent samples. After a post-HIPing treatment, the optical transmittance of the samples with a pre-sintering step was substantially improved to higher levels in the visible and the IR wavelengths compared to that of a sample which does not undergo pre-sintering. The corresponding mechanism was revealed by microstructural analyses.</P>

Fabrication and properties of La₂O₃-doped transparent yttria ceramics by hot-pressing sintering

Gan, Lin,Park, Young-Jo,Zhu, Lin-Lin,Go, Shin-Il,Kim, Haneul,Kim, Jin-Myung,Ko, Jae-Woong Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.695 No.-

<P><B>Abstract</B></P> <P>In this work, highly transparent La<SUB>2</SUB>O<SUB>3</SUB>-doped yttria ceramics were fabricated by a hot-pressing method. The effects of the La<SUB>2</SUB>O<SUB>3</SUB> doping concentration (0–17 at.%) on the optical transmittance, microstructures, microhardness, and thermal conductivity levels of the transparent yttria were investigated in an effort to develop a user's choice guide pertaining to the optical, mechanical, and thermal properties. The optimal La<SUB>2</SUB>O<SUB>3</SUB> doping concentration for the optical transmittance was found to be 12 at.%, leading to in-line transmittance levels of 68.9% at 400 nm and 81.9% at 1100 nm (2 mm thick). The microhardness changed from 6.82 to 7.66 GPa and was found to be closely dependent on the grain sizes of the samples, which varied from 3.55 μm to 0.95 with changes in the La<SUB>2</SUB>O<SUB>3</SUB> doping concentration. The biaxial flexure strength of a hot-pressed sample with an average grain size of 1.46 μm exceeded that of a conventionally pressureless-sintered coarse-grained sample (grain size 40.82 μm) by 94.4%. The thermal conductivity showed a significant decrease from 16.40 to 5.71 W/mK with an increase in the La<SUB>2</SUB>O<SUB>3</SUB> doping concentration from 0 to 17 at.%. Potential applications of the transparent yttria ceramics with different compositions were suggested based on the combination of the optical, mechanical, and thermal properties.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly transparent La-doped yttria ceramics were prepared by hot pressing. </LI> <LI> Effects of La concentration on transmittance, microstructure were studied. </LI> <LI> Effects of La concentration on thermal conductivity were studied. </LI> <LI> Microhardness and biaxial flexure strength of the samples were studied. </LI> </UL> </P>

Optical and thermo-mechanical properties of fine-grained transparent yttria ceramics fabricated by hot-press sintering for infrared window applications

Gan, Lin,Park, Young-Jo,Zhu, Lin-Lin,Kim, Ha-Neul,Ko, Jae-Woong,Kim, Hai-Doo Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.11

<P><B>Abstract</B></P> <P>In this work, highly transparent yttria ceramics Φ = 55 mm in size were fabricated by a hot-pressing method with 1 at.% ZrO<SUB>2</SUB> or 12 at.% La<SUB>2</SUB>O<SUB>3</SUB> as a sintering additive. For a 4-mm-thick specimen doped with ZrO<SUB>2</SUB>, the in-line transmittance reaches 71.1% at 400 nm and 80.9% at 1100 nm, and the transmittance of the La<SUB>2</SUB>O<SUB>3</SUB>-doped specimen is comparable to that of the ZrO<SUB>2</SUB>-doped specimen. By means of the relatively low sintering temperature of 1600 °C, the present samples exhibited very fine microstructures (<2 μm), giving rise to excellent mechanical strength levels (∼200 MPa). With regard to the 1 at.% ZrO<SUB>2</SUB>-doped specimen, the combination of high strength and high thermal conductivity (∼10 W/m K) substantially improved parameters related to the thermal shock resistance. The results of this study indicate that the hot-pressed transparent yttria ceramic doped with 1 at.% ZrO<SUB>2</SUB> is optically, mechanically, and thermally suitable for high-temperature IR window applications.</P>

Factor Graph-based Multipath-assisted Indoor Passive Localization with Inaccurate Receiver

( Ganlin Hao ),( Nan Wu ),( Yifeng Xiong ),( Hua Wang ),( Jingming Kuang ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.2

Passive wireless devices have increasing civilian and military applications, especially in the scenario with wearable devices and Internet of Things. In this paper, we study indoor localization of a target equipped with radio-frequency identification (RFID) device in ultra-wideband (UWB) wireless networks. With known room layout, deterministic multipath components, including the line-of-sight (LOS) signal and the reflected signals via multipath propagation, are employed to locate the target with one transmitter and a single inaccurate receiver. A factor graph corresponding to the joint posterior position distribution of target and receiver is constructed. However, due to the mixed distribution in the factor node of likelihood function, the expressions of messages are intractable by directly applying belief propagation on factor graph. To this end, we approximate the messages by Gaussian distribution via minimizing the Kullback-Leibler divergence (KLD) between them. Accordingly, a parametric message passing algorithm for indoor passive localization is derived, in which only the means and variances of Gaussian distributions have to be updated. Performance of the proposed algorithm and the impact of critical parameters are evaluated by Monte Carlo simulations, which demonstrate the superior performance in localization accuracy and the robustness to the statistics of multipath channels.

Spatial Prediction of Soil Variables Based on Primary Terrain Attributes in a Gentle Area

Xiaodong Song,Ganlin Zhang,Feng Liu 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

A Fault Diagnosis Method of Oil-Immersed Transformer Based on Improved Harris Hawks Optimized Random Forest

Yi Lingzhi,Jiang Ganlin,Zhang Guoyong,Yu Wenxin,Guo You,Sun Tao 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.4

In order to improve the accuracy and reliability of fault diagnosis for oil-immersed transformers, a fault diagnosis method for oil-immersed transformers based on improved Harris Hawks optimized random forest is proposed in this paper. First, logistic chaotic mapping is used to adjust the key parameters of the algorithm; then a nonlinear energy factor adjustment strategy is used to control the algorithm to transition from global search to local search; fi nally, the method of Gaussian mutation is introduced to strengthen the local search ability, and when the algorithm is stagnant, fi refl y perturbation is performed on the optimal solution to make the algorithm jump out of local optimum. The number of n_trees and n_layers of the random forest are jointly optimized by the improved Harris Hawks optimization algorithm, and the fault diagnosis model of oil-immersed transformer is established. The noncoded ratios of dissolved characteristic gases in oil are used as the characteristic input of the diagnosis model to obtain the fi nal diagnosis results. Compared with other models and verifi ed by examples, the results show that the proposed method has the advantage of high diagnostic accuracy and has certain practical engineering application value.

Distributed Target Localization with Inaccurate Collaborative Sensors in Multipath Environments

( Yuan Feng ),( Qinsiwei Yan ),( Po-hsuan Tseng ),( Ganlin Hao ),( Nan Wu ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.5

Location-aware networks are of great importance for both civil lives and military applications. Methods based on line-of-sight (LOS) measurements suffer sever performance loss in harsh environments such as indoor scenarios, where sensors can receive both LOS and non-line-of-sight (NLOS) measurements. In this paper, we propose a data association (DA) process based on the expectation maximization (EM) algorithm, which enables us to exploit multipath components (MPCs). By setting the mapping relationship between the measurements and scatters as a latent variable, coefficients of the Gaussian mixture model are estimated. Moreover, considering the misalignment of sensor position, we propose a space-alternating generalized expectation maximization (SAGE)-based algorithms to jointly update the target localization and sensor position information. A two dimensional (2-D) circularly symmetric Gaussian distribution is employed to approximate the probability density function of the sensor's position uncertainty via the minimization of the Kullback-Leibler divergence (KLD), which enables us to calculate the expectation step with low computational complexity. Moreover, a distributed implementation is derived based on the average consensus method to improve the scalability of the proposed algorithm. Simulation results demonstrate that the proposed centralized and distributed algorithms can perform close to the Monte Carlo-based method with much lower communication overhead and computational complexity.

Toward a Global System of Soil Horizon Nomenclature

Curtis Monger,Lucia Helena C. Anjos,Ganlin Zhang,Sergey Goryachkin,Ben Harms,Peter Schad,Catherine Fox,Sonn Yeon-Kyu 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6