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A Sequential Selection Normalized Subband Adaptive Filter with Variable Step-Size Algorithms
Shin, JaeWook,Baek, Hyun Jae,Park, Bum Yong,Cho, Jaegeol Hindawi Limited 2018 Mathematical problems in engineering Vol.2018 No.-
<P>This letter proposes a sequential selection normalized subband adaptive filter (SS-NSAF) in order to reduce the computational complexity. In addition, a variable step-size algorithm is also proposed using the mean-square deviation analysis of the SS-NSAF. To enhance the performance in terms of the convergence speed, we propose an improved variable step-size SS-NSAF using a two-stage concept. The simulation results show the low computational complexity and low misalignment errors using the proposed algorithm.</P>
Shin, Jaewook,Cho, EunAe American Chemical Society 2018 Chemistry of materials Vol.30 No.10
<P>Si, the high-capacity anode for Li-ion battery (LIB), has intrinsic 300% volume changes limiting its commercial application. The volume change leads to particle pulverization that results in loss of electrical contacts. Various nanostructures are proposed to avoid the pulverization, but the commercialization is still a distant future. Recently, Al<SUB>2</SUB>O<SUB>3</SUB> has demonstrated its ability to enhance electrochemical cycling performance. However, a comprehensive mechanistic role of the Al<SUB>2</SUB>O<SUB>3</SUB> has not been well-understood. Here, we have combined electrochemical and chemical agitation tests to propose two novel mechanisms: Si agglomeration and a protective role of the Al<SUB>2</SUB>O<SUB>3</SUB>. LiPF<SUB>6</SUB>, the common Li salt of the LIB electrolyte, decomposes and forms HF that etches the native oxide layer then forms a labile Si-H surface. Because of the labile Si-H surfaces, the Si particles agglomerate during the volume changes. The Si agglomeration has a detrimental effect on the cycling performance associated with the loss of electrical contacts. On the other hand, in the presence of the Al<SUB>2</SUB>O<SUB>3</SUB>, the Al<SUB>2</SUB>O<SUB>3</SUB> consumes the HF, protecting the native oxide layer that resists the agglomeration. Thus, the Si particles with Al<SUB>2</SUB>O<SUB>3</SUB> are better-dispersed. The Al<SUB>2</SUB>O<SUB>3</SUB> allows the better Si dispersion during electrochemical cycles, resulting in improved capacity retention.</P> [FIG OMISSION]</BR>
Jaewook Shin,Min-Oh Kim,Sungmin Cho,Dong-Hyun Kim IEEE 2017 IEEE transactions on medical imaging Vol.36 No.8
<P>Magnetic resonance electrical property tomography (MREPT) is a technique used to extract the electrical properties of tissues (conductivity in particular) using a magnetic resonance imaging system. In this paper, we propose an improved data acquisition scheme for the electrical property tomography technique by utilizing T-2 modulation in fast spin echo (FSE) imaging. This technique was motivated by a numerical analysis of conductivity reconstruction in the frequency domain; results reveal the spatial frequency-dependent noise texture of conventional methods. A data-acquisition scheme using the FSE sequence was formulated to concentrate the signal within a specific frequency range where notable noise amplification is observed in the conventional method. Through numerical studies, the performance of the proposed acquisition was investigated. Furthermore, a compensation scheme was applied to reduce quantification errors due to tissuespecific T-2 modulation, which is inherent in FSE imaging. The technique was applied to phantom and in vivo experiments. Results showed improved conductivity contrasts in both experiments, as compared with conventional MREPT methods.</P>
Jaewook Shin,Hyunchol Shin IEEE 2010 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS PART 1 R Vol.57 No.7
<P>A VCO frequency calibration technique suitable for a wideband fractional-N PLL is presented. It provides a fast and high-precision search for an optimal discrete tuning curve of an LC VCO during the coarse tuning process in a fractional-N PLL. A high-speed frequency error detector (FED) converts the VCO frequency to a digital value and computes the exact frequency difference from a target frequency. A minimum error code finder finds an optimal code that is closest to the target frequency. Due to the pure digital domain operation, a ΔΣ modulator in PLL can be deactivated during the calibration process, which makes this technique fast and accurate especially for a ΔΣ fractional-N PLL. We achieve a single-bit calibration time of only kT<SUB>REF</SUB> for obtaining a frequency resolution of f<SUB>REF</SUB>/k, and compared to the conventional techniques, which is the best performance in terms of the calibration time versus resolution. Such fast VCO frequency calibration can greatly reduce the total lock time in a PLL. A 2.3-3.9 GHz fractional-N PLL employing the proposed calibration technique is implemented in 0.13 μm CMOS. Successful operation is verified through experimental results. The measured calibration time for a 6-bit capbank is 1.09 and 2.03 μs for a frequency resolution of 19.2 and 4.8 MHz, respectively.</P>
Variable Step-Size Sign Subband Adaptive Filter
JaeWook Shin,JinWoo Yoo,PooGyeon Park IEEE 2013 IEEE signal processing letters Vol.20 No.2
<P>This letter proposes a variable step-size sign subband adaptive filter (SSAF) based on the minimization of mean-square deviation (MSD). In the process of minimizing the MSD, because it is not feasible to know the exact value of the MSD, the step size is derived by minimizing the upper bound of the MSD in each iteration. The proposed algorithm uses this step size in the SSAF update equation so as to improve the filter performance in terms of the convergence rate and the steady-state estimation error. The proposed algorithm is tested in a system-identification scenario that includes impulsive noise. Simulation results show that the proposed algorithm performs better than the previous algorithms.</P>
Shin Yongbeom,박명남,Lee Jaewook,Kang Kibyung,Wang Sungki,Lee Eunsung,Song Seongkeun,Shin Dongil 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.6
In the catalytic reforming process, aromatic yield is a standard for evaluating the production quality of the process, and studies are underway to improve productivity by optimizing the cost and energy. In particular, the activity and lifetime prediction of reforming catalysts can contribute to overall process efficiency improvement, such as product quality, productivity, and predictive maintenance. However, it is difficult to predict real-time catalyst activity and lifetime according to changes in process operation with the existing method that requires experimental data. In this study, a multiple linear regression (MLR) model and GRU model with the real process operating data are proposed for long-term plant operation and optimization in the counter-current continuous catalytic reforming. The MLR-GRU model predicts catalyst performance degradation and lifetime according to operating conditions by defining a new variable, reforming catalyst activity. The proposed model can predict the future reformate yield with an error of less than 1%. As a result of predicting the catalyst lifetime according to various operating temperatures, feed flow patterns, and feed quality, the feed flow rate had the greatest influence on the catalyst lifetime profile. In terms of the amount of produced reformate oil, the case with maximum feed rate is the worst (−25.6%); on the other hand, the case with minimum feed rate is the best (+11.4%). Thus, it is important to establish an appropriate production plan of the produced reformate oil. The model proposed in this study can predict the reformate yield and lifetime, reflecting the degradation of catalyst performance according to the operating profile in real-time, which is expected to improve productivity by production scheduling, optimization, and predictive maintenance.
Thermal Characteristics of Various Substrates at Different Moisture Contents under the Pipe Coolin
Jaewook Shin,Byungkwan Lee,Minh Duy Pham,Hyunseung Hwang,Meiyan Cui,Hyein Lee,Jeesang Myung,Changhoo Chun 한국원예학회 2021 한국원예학회 학술발표요지 Vol.2021 No.10
Root-zone pipe cooling is a method to overcome the high air temperature in the summer season without high cooling load and cost in the greenhouse by using cooling pipes in close contact with the substrate. Few studies have been conducted on the substrate’s thermal characteristics and suitability for pipe cooling. We investigated the thermal characteristics of four substrates; coir, commercial growing media (Plant World; Nong Woo Bio, Suwon, Korea), perlite, and rockwool at two moisture contents; 40 and 80% (w/w). A silicone tube (8 mm in diameter) was coiled six times inside a container (170 mm in diameter), and chilled water of 15°C was circulated with a rate of 2.7 L min<SUP>-1</SUP>. Smaller pots (150 mm in diameter, 1.4 L) were filled with each type of substrates and adjusted to the moisture content of 40 or 80%. The smaller pot was then inserted into the container with the cooling pipe and cooled for 80 min. During the study, the average air temperature and relative humidity was set as 25°C and 63%, respectively. The temperature was measured with thermocouples at four positions (upper, middle, lower, and side points). The pipe cooling method reduced the temperature of substrate by 7.9–16.4°C depending on the type and moisture content showing that this is an effective method for controlling root-zone temperature. The average cooling rate (°C min<SUP>-1</SUP>) of perlite was the fastest at both moisture contents. At the moisture content of 40%, rockwool showed the second fastest cooling rate after perlite, followed by commercial growing media and coir. At the moisture content of 80%, commercial growing media showed the second fastest cooling rate, followed by coir and rockwool. In all substrates, the cooling rate was faster in the moisture content of 40% treatment than in 80% treatment. The temperature difference between the center (the mean value of upper, middle, and lower positions) and the side position of the substrate was the largest in coir in both moisture content treatments, followed by commercial growing media. The temperature difference between the center and the side positions at the moisture content of 40% was greater than that at 80% for all substrates. The substrate with a faster cooling rate showed a tendency to have a smaller temperature difference between the center and the side positions indicating a more uniform internal heat distribution. We expect that the thermal characteristics of substrates obtained from the study could help to select optimal substrates for energy-efficient and effective root-zone cooling methods to produce horticultural plants in the greenhouse.