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Multiple phase transitions in block copolymer blends and pressure effects on these transitions
Lee, Yonghoon,Jo, Seongjun,Lee, Wooseop,Lee, Hoyeon,Han, Young Soo,Ryu, Du Yeol Elsevier 2017 Polymer Vol.112 No.-
<P><B>Abstract</B></P> <P>We sought to identify an evident enthalpic-driven transition below an entropic-driven closed-loop phase transition by studying the phase behavior in miscible binary block copolymer (BCP) blends of a polystyrene-<I>b</I>-poly (<I>n</I>-butyl methacrylate) (PS-<I>b</I>-P<I>n</I>BMA) and a deuterated polystyrene-<I>b</I>-poly (<I>n</I>-hexyl methacrylate) (<I>d</I>PS-<I>b</I>-P<I>n</I>HMA), using small-angle x-ray scattering (SAXS) and depolarized light scattering (DPLS). Intriguingly, an order-to-disorder transition (ODT) below the closed-loop transition consisting of a lower disorder-to-order transition (LDOT) and an upper order-to-disorder transition (UODT) was observed in the BCP blends of an asymmetric (PS-rich) PS-<I>b</I>-P<I>n</I>BMA and a symmetric <I>d</I>PS-<I>b</I>-P<I>n</I>HMA. Multiple phase transitions, previously undiscovered in BCP system, were attributed to a delicate balance in the free energy of the dispersive intermolecular interactions, the entropic compressibility, and the combinatorial entropy of mixing at an experimental temperature range between the glass transition temperature (<I>T</I> <SUB>g</SUB>) and degradation temperature (<I>T</I> <SUB>d</SUB>). We also characterized the effects of hydrostatic pressure on the transition temperatures to determine the thermodynamic origins of each phase transition.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Phase behavior in miscible binary BCP blends of weakly interacting PS-<I>b</I>-P<I>n</I>BMA/<I>d</I>PS-<I>b</I>-P<I>n</I>HMA. </LI> <LI> Multiple phase transitions displaying an ODT to a LDOT and an UODT (in the closed-loop transition) upon heating. </LI> <LI> 3D phase transition diagram of the BCP blends based on transition behavior. </LI> <LI> Pressure effects on the transition temperatures to evaluate the pressure coefficient (<I>dT/dP</I>). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Effective Multiplexing Method for Conditional Access System in Terrestrial DMB
YongHoon Lee,Gwangsoon Lee,Jinhwan Lee,Soo In Lee,김남 한국전자통신연구원 2008 ETRI Journal Vol.30 No.6
This letter proposes a conditional access system (CAS) suitable for use in terrestrial digital multimedia broadcasting (T-DMB), based on an effective multiplexing method to provide encrypted T-DMB services. Specifically, the proposed multiplexing method for a CAS is designed to reduce the additional bit rate while assuring easy access to the designated encrypted services. Finally, the performance of the implemented CAS is confirmed through implementation and a broadcasting experiment under various service environments.
Yonghoon Choi,Nayoung Kim,Gi Tark Noh,Ju Yup Lee,Dong Ho Lee 거트앤리버 소화기연관학회협의회 2020 Gut and Liver Vol.14 No.1
Background/Aims: The Flos Lonicera extract GCWB104 has been shown to have significant protective effects against gastritis and gastric ulcers in vivo. The aim of this study was to investigate the efficacy and safety of GCWB104 in subjects with functional dyspepsia (FD). Methods: In this single-center, double-blind, randomized clinical trial, 92 subjects diagnosed with FD using the Rome III criteria were allocated to either the test group (300 mg of GCWB104, containing 125 mg of Flos Lonicera extract, twice daily) or the placebo group (300 mg placebo, twice daily). The total score improvement on the Gastrointestinal Symptom Rating Scale (GSRS) for individual symptoms, changes in antioxidant levels, changes in dyspepsia-related quality of life according to the Nepean Dyspepsia Index (NDI), and adverse effects were compared before and after 8 weeks of treatment. Results: The differences in total GSRS scores and score improvements after 8 weeks of treatment were significant between the GCWB104 and control groups (p=0.0452 and p=0.0486, respectively). Thirteen of 15 individual symptoms on the GSRS improved in the GCWB104 group, while six symptoms improved in the control group. In addition, statistically significant changes in rumbling, loose stool, and stool urgency were observed in the GCWB104 group. Blood 8-hydroxy-2’-deoxyguanosine (8-OHdG) levels, known as antioxidants, showed significant reductions after 8 weeks of administration of GCWB104. There were no adverse events related to treatment with GCWB104. Conclusions: GCWB104 safely contributed to improvements in mild to moderate FD and irritable bowel syndrome symptoms. Antioxidant effects of GCWB104 were also suggested (Clinicaltrials.gov number NCT04008901).
Suppression of the Methyl Radical Loss from Acetone Cation within (CH3COCH3)nCH3COCH3 + Clusters
Yonghoon Lee,Myoung-Kyu Oh,Sung-Chul Choi,고도경,Jongmin Lee 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.8
We have investigated the photophysics of the acetone radical cation in the vacuum ultraviolet energy region by multiphoton ionization combined with time-of-flight mass spectrometry in a cluster beam. We have found that the loss of methyl radical from the acetone radical cations is remarkably suppressed at 10.5 eV when they are solvated by a few neutral acetone molecules. The cluster ion mass spectra obtained by nanosecond and picosecond laser pulses reveal that there are intermolecular processes, occurring in several tens of picoseconds, which are responsible for the survival of the acetone cations in clusters. This remarkable solvation effect on the yield of the methyl radical loss from the acetone cation can be rationalized by the intracluster vibrational energy redistribution and the self-catalyzed enolization which compete with the methyl radical loss process.
Elemental analysis of rice using laser-ablation sampling: Determination of rice-polishing degree
Yonghoon Lee 한국분석과학회 2024 분석과학 Vol.37 No.1
In this study, laser-induced breakdown spectroscopy (LIBS) was used to estimate the degree of ricepolishing. As-threshed rice seeds were dehusked and polished for different times, and the resulting grains wereanalyzed using LIBS. Various atomic, ionic, and molecular emissions were identified in the LIBS spectra. Theircorrelation with the amount of polished-off matter was investigated. Na I and Rb I emission line intensitiesshowed linear sensitivity in the widest range of polished-off-matter amount. Thus, univariate models based onthose lines were developed to predict the weight percent of polished-off matter and showed 3-5 % accuracyperformances. Partial least squares-regression (PLS-R) was also applied to develop a multivariate model usingSi I, Mg I, Ca I, Na I, K I, and Rb I emission lines. It outperformed the univariate models in prediction accuracy(2 %). Our results suggest that LIBS can be a reliable tool for authenticating the degree of rice polishing, whichis closed related to nutrition, shelf life, appearance, and commercial value of rice products.
Lee, Seungjin,Lim, Jaehyuk,Oh, Sangyeol,Kim, Yonghoon,Oh, Dan,Lee, Jaehoon IEEE 2019 IEEE transactions on components, packaging, and ma Vol.9 No.4
<P>In this paper, we propose a method to suppress differential-to-common-mode conversion noise from right-angle bent differential lines by installing a mushroom structure on the narrow inner line. We assessed the mode conversion noise suppression characteristics of the proposed structure by analyzing dispersion diagrams. The proposed structure exhibits differential-to-common-mode conversion ( <TEX>$S_{cd21}$</TEX>) below −20 dB up to 6 GHz, while <TEX>$S_{cd21}$</TEX> of conventional right-angle bent differential lines is only maintained below −20 dB for frequencies up to 1.04 GHz. In addition, we suggest that further enhancements of the mode conversion suppression bandwidth can be achieved by installing multiple distributed mushroom structures on right-angle bent differential lines. The use of multiple distributed mushrooms enabled us to achieve a wider frequency bandwidth by compensating more fully for the phase difference between the inner and outer lines. Therefore, the right-angle bent differential lines with multiple distributed mushrooms can suppress mode conversion noise under −20 dB up to 10 GHz. We assessed the performance of our proposed structure by conducting measurements in both the frequency and time domains. We obtained a good agreement between our experimental and numerical results. In addition, we measured eye diagrams to demonstrate that the proposed structures suppress differential-to-common-mode conversion noise without degrading the differential signaling quality.</P>
Lee, Yonghoon,Han, Song-Hee,Nam, Sang-Ho SAGE Publications 2017 APPLIED SPECTROSCOPY Vol.71 No.9
<P>We report soft independent modeling of class analogy (SIMCA) analysis of laser-induced plasma emission spectra of edible salts from 12 different geographical origins for their classification model. The spectra were recorded by using a simple laser-induced breakdown spectroscopy (LIBS) device. Each class was modeled by principal component analysis (PCA) of the LIBS spectra. For the classification of a separate test data set, the SIMCA model showed 97% accuracy in classification. An additional insight could be obtained by comparing the SIMCA classification result with that of partial least squares discriminant analysis (PLS-DA). Different from SIMCA, the PLS-DA classification accuracy seems to be sensitive to addition of new sample classes to the whole data set. This indicates that the individual modeling approach (SIMCA) can be an alternative to global modeling (PLS-DA), particularly for the classification problems with a relatively large number of sample classes.</P>
Lee, Dong Hyun,Lee, Hoyeon,Lee, Yonghoon,Kim, Yoonkeun,Ryu, Du Yeol American Chemical Society 2014 Macromolecules Vol.47 No.6
<P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2014/mamobx.2014.47.issue-6/ma402535w/production/images/medium/ma-2013-02535w_0006.gif'></P>