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Modified RLS Algorithm and Its Application to Channel Estimation for CDMA Systems
CHOI, Jihoon,JUNG, Young-Ho The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.5
<P>A new adaptive algorithm is proposed by introducing some modifications to the recursive least squares (RLS) algorithm. Except for the noise variance, the proposed algorithm does not require any statistics or knowledge of the desired signal, thus, it is suitable for adaptive filtering for channel estimation in code division multiple access (CDMA) systems in cases where the standard RLS approach cannot be used. A theoretical analysis demonstrates the convergence of the proposed algorithm, and simulation results for CDMA channel estimation show that the proposed algorithm outperforms existing channel estimation schemes.</P>
Linear Fresnel Lens for a Solar Cell with above 85% Focal Efficiency
Jihoon Choi,Heeso Noh,Hyeri Jang,Jeong Seok Kang 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.8
We designed a linear Fresnel lens (LFL) for harvesting solar energy. The optimized LFL was fabricated with dimensions of 100 (W) × 100 (H) × 5 (T) mm^3, a focal length of 100 mm, and a fixed pitch size of 500 μm. The maximum focal efficiency is approximately 91%, and the half width at half maximum (HWHM) value of the focus size is approximately 130 μm. We also investigated the robustness of the LFL to changes in the incident angle, draft angle, and detection position. Simulations revealed a focal efficiency above 85% with an incident angle up to 1°, a draft angle up to 10°, and a detection position up to ±10 mm. We fabricated the LFL by using an injection molding process. The fabricated lens had a maximum focal efficiency of approximately 88% and a full width at half max (FWHM) of about 2.5 mm.
Differential Cytotoxic Effects of Jaspine B in Various Cancer Cells
Jihoon Lee(이지훈),Kwangik Choi(최광익),Mihwa Kwon(권미화),Dongjoo Lee(이동주),Min-Koo Choi(최민구),Im-Sook Song(송임숙) 한국생명과학회 2016 생명과학회지 Vol.26 No.12
Jaspine B는 석회해면류에서 추출된 sphingosine유도체로 인간 암세포에서의 항암활성이 보고되었다. 그러므로 본 연구는 다양한 인간 암세포주에서 항암활성을 비교하고, 암세포주에서의 Jaspine B의 농도를 측정하여 항암활성과의 연관성을 확인하고자 하였다. 항암활성은 MTT 방법을 이용하여 측정하였고, EC50 값으로 표현하였다. 암세포주내 Jaspine B의 농도는 LC-MS/MS를 이용하여 분석하였다. 항암활성은 세포주마다 다양하게 나타났는데, 유방암과 흑색종 세포주에서 항암활성이 높게 나타났으며(EC50 각각 2.3 μM과 2.6 μM), 신장암세포주에서는 EC50 값이 29.4 μM이었다. 암세포주에서의 EC50 값은 동일한 세포에서의 Jaspine B 농도와 높은 상관성을 나타내었으며(r=0.838), 암세포내 약물농도를 조절하는 것으로 잘 알려진 P-glycoprotein과 breast cancer resistance protein 등의 배출수송계와는 관련이 없음을 확인하였다. 이상의 결과는 세포내 약물농도를 높게 유지하는 것이 항암활성에 매우 중요하며, 세포내 약물농도가 암세포주에 따라 다른 약효를 보이는 원인으로 사료된다. Jaspine B is an anhydrophytosphingosine that is isolated from a marine sponge. Because of its structural similarity to sphingosine, it shows anti-cancer effects in human carcinomas. Therefore, this study aims to investigate its anti-proliferative effect on various cancer cells and to correlate its association with the intracellular accumulation of Jaspine B in relevant cancer cells. The anti-proliferative effect of Jaspine B in various cancer cells was determined by a cell viability test, and the intracellular concentration of Jaspine B in relevant cancer cells was determined using mass spectrometry coupled with liquid chromatography. The correlation coefficient and p value between the cytotoxicity and the cell accumulation of Jaspine B were determined using SPSS 16.1. The cytotoxicity of Jaspine B varied depending on the type of cancer cell when compared the EC50 values of Jaspine B. Breast and melanoma cancer cells were susceptible to Jaspine B, whereas renal carcinoma cells were resistant. The intracellular concentrations of Jaspine B had a reciprocal correlation with the EC50 values in the same cells (r = 0.838). The results suggested that the anti-proliferative effect of Jaspine B was associated with the cellular accumulation of this compound. However, Jaspine B was not a substrate for P-glycoprotein and breast cancer resistance protein, as major efflux pumps caused multidrug resistance. The maintenance of a high intracellular concentration is crucial for the cytotoxic effect of Jaspine B; however, efflux pumps may not be a controlling factor for Jaspine B-related resistance in cancer cells.
Low-Complexity Multiuser MIMO Precoder Design Under Per-Antenna Power Constraints
Choi, Jihoon,Han, Suyong,Joung, Jingon IEEE 2018 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.67 No.9
<P>A new precoder design method is proposed for multi-input multioutput (MIMO) systems with per-antenna power constraints (PAPCs). In the proposed scheme, the optimal zero-forcing (ZF) based precoder maximizing the sum rate is evaluated for MIMO systems under the conventional sum power constraint (SPC), after which a new ZF-based precoder conforming to the PAPCs is designed by finding the linear precoder closest to the optimal ZF-based SPC precoder. Using the proposed design procedure, we derive an iterative algorithm based on the modified Newton's method to construct a PAPC precoder for a multiuser MIMO system. The complexity order of the proposed method is compared with those of the existing precoding schemes, and it is shown through numerical simulations that the proposed PAPC precoder achieves near-optimal performance while reducing the power consumption at macrocell base stations.</P>
On the Calculation of the Maximal MOT Throughput in T-DMB
Jihoon Choi,Donghwan Lee,Jieun Yu,Kyunghwi Kim,Wonjun Lee IEEE 2007 IEEE transactions on consumer electronics Vol.53 No.3
<P>Digital multimedia broadcasting (DMB) is one of burgeoning communication technologies, which can provide audio, video, and data services to mobile terminals using broadcasting infrastructures. Data services in terrestrial- digital multimedia broadcasting (T-DMB) inherently have the disadvantage of retransmitting a lot of data unnecessarily for reliability. This paper proposes a novel optimized transmission policy using segment size and repetition number variability, which maximizes the object- level throughput as well as improves reliability. The theoretical modeling and simulation results demonstrate that our policy provides a throughput gain over the conventional protocol.</P>
Wireless Powered Information Transfer Based on Zero-Forcing for Multiuser MIMO Systems
Choi, Jihoon,Song, Choonggeun,Joung, Jingon IEEE 2018 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.67 No.9
<P>A zero-forcing (ZF)-based transmission method is proposed for a wireless powered communication network (WPCN) with multiuser multi-input multi-output (MU-MIMO) channels. We formulate the max–min user rate optimization problem based on ZF-based uplink transmission, under the transmit power constraints determined by the downlink power transfer, and derive a Newton-like iterative algorithm to find the optimal solution of the proposed problem. Using the proposed ZF-based method, we design a downlink energy beamformer, and optimize the uplink power allocation vector, precoder, and combiner in terms of the max–min user rate for a MU-MIMO WPCN system. Numerical simulations show that the proposed method provides at least 3 dB signal-to-noise ratio gain compared to the conventional transmission schemes for WPCN. Moreover, through complexity analysis and simulations, it is shown that the proposed method can reduce at least 92% of the computation load in terms of runtime with moderate achievable rate loss, compared to the optimal method obtained by the interior-point method.</P>
Jihoon Kim,Joo Myung Lee,Taek Kyu Park,Jeong Hoon Yang,Young Bin Song,Jin-Ho Choi,Seung-Hyuk Choi,Hyeon-Cheol Gwon,Sang Hoon Lee,Joo-Yong Hahn 대한의학회 2020 Journal of Korean medical science Vol.35 No.1
Background: Although current guidelines recommend noninvasive stress tests prior to elective percutaneous coronary intervention (PCI), it is unknown whether antecedent exercise stress test (EST) affects the outcomes of patients undergoing PCI for stable ischemic heart disease (SIHD). This study aimed to investigate long-term outcomes in patients undergoing elective PCI with or without EST. Methods: We studied 2,674 patients undergoing elective PCI using drug-eluting stents for SIHD. Patients were divided into the 2 groups: the test group underwent EST with a positive result within 180 days prior to PCI (n = 668), whereas the non-test group did not undergo any noninvasive stress tests (n = 2,006). The primary outcome was all-cause death or myocardial infarction (MI). Results: Over 5 years after the index PCI, the risk of all-cause death or MI was significantly lower in the test group than in the non-test group in overall population (3.3% vs. 10.9%; adjusted hazard ratio [HR], 0.34; 95% confidence interval [CI], 0.22–0.55; P < 0.001), and in propensity score-matched population (668 pairs) (3.3% vs. 6.3%; adjusted HR, 0.52; 95% CI, 0.30–0.89; P = 0.018). However, the incidence of any revascularization was similar between the 2 groups in overall (16.7% vs. 16.8%; adjusted HR, 0.99; 95% CI, 0.79–1.25; P = 0.962) and matched population (16.7% vs. 18.3%; adjusted HR, 0.91; 95% CI, 0.70–1.19; P = 0.509). Conclusion: Patients who underwent elective PCI with EST had a reduced risk of all-cause death or MI than those undergoing PCI without stress tests.