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衝擊波動 重疊原理에 의한 耐衝擊性 3重壁構造 Polymer
申容珍,崔勝平,梁京承,白昌鉉 朝鮮大學校 自然科學硏究所 1995 自然科學硏究 Vol.18 No.1
In thermoplasticity polymer, mean molecular weight and molecular weight distribution are the important factors which effect the physical property. If impact strength(I.S-) is high, tensile strength(T.S.) and flating weight(F.W-) are low. Because of the reciprocal relation I.S. and T.S. there set a limit to satisfy I.S. and T.S. in single matter at the same time. Applying the superposition principle to the polymer, extemal impact wave pulse on the 3-1ayered stmcture may be changed to the transmitted wave and reflected wave, and then separated waves lose the mechanical energy to the S-layered structure which contains different molecular weight. There is the dispersion and attenuation of the impact energy, hence at the low temperature impact strength and tensile strength synchronously are high.
Room-Temperature Ring-Opening of Quinoline, Isoquinoline, and Pyridine with Low-Valent Titanium
Baek, Seung-yeol,Kurogi, Takashi,Kang, Dahye,Kamitani, Masahiro,Kwon, Seongyeon,Solowey, Douglas P.,Chen, Chun-Hsing,Pink, Maren,Carroll, Patrick J.,Mindiola, Daniel J.,Baik, Mu-Hyun American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.36
<P>The complex (PNP)Ti=(CHBu)-Bu-t((CH2Bu)-Bu-t) (PNP = N[2-P(i)p(r2)-4-methylphenyl](2-)) dehydrogenates cyclohexane to cyclohexene by forming a transient low-valent titanium-alkyl species, [(PNP)Ti((CH2Bu)-Bu-t)], which reacts with 2 equiv of quinoline (Q) at room temperature to form (H3CBu)-Bu-t and a Ti(IV) species where the less hindered C-2=N-1 bond of Qis ruptured and coupled to another equivalent of Q, The product isolated from this reaction is an imide with a tethered cycloamide group, (PNP)Ti=N[C18H13N] (1). Under photolytic conditions, intramolecular C-H bond activation across the imide moiety in 1 occurs to form 2, and thermolysis reverses this process. The reaction of 2 equiv of isoquinoline (Iq) with intermediate [(PNP)Ti((CH2Bu)-Bu-t)] results in regioselective cleavage of the C-I=N-2 and C-1-H bonds, which eventually couple to form complex 3, a constitutional isomer of 1. Akin to 1, the transient [(PNP)Ti((CH2Bu)-Bu-t)] complex can ring-open and couple two pyridine molecules, to produce a close analogue of 1, complex (PNP)Ti=N[C10H9N] (4). Multinudear and multidimensional NMR spectra confirm structures for complexes 1-4, whereas solid-state structural analysis reveals the structures of 2, 3, and 4. DFT calculations suggest an unprecedented Mechanism for ring-opening of Q wheat the reactive intermediate in the low-spin manifold crosses over to the high-spin surface to access a low-energy transition state but returns to the low-spin surface immediately. This double spin-crossover constitutes a rare example of a two-state reactivity, which is key for enabling the reaction at room temperature. The regioselective behavior of Iq ring-opening is found to be due to electronic effects, where the aromatic resonance of the bicycle is maintained during the key C-C coupling event.</P>
Effect of secondary phase particles on the tensile behavior of Mg-Zn-Ca alloy
Baek, Seung Mi,Park, Hyung Keun,Yoon, Jae Ik,Jung, Jaimyun,Moon, Ji Hyun,Lee, Seok Gyu,Kim, Jae H.,Kim, Taek Soo,Lee, Sunghak,Kim, Nack J.,Kim, Hyoung Seop Elsevier 2018 Materials science & engineering. properties, micro Vol.735 No.-
<P><B>Abstract</B></P> <P>In the present study, the effect of secondary phase particles and deformation localization on tensile behaviors of Mg-Zn-Ca alloy were investigated using micro-digital image correlation method. To isolate the effect of the secondary phase particles on tensile behavior, the fractions of the secondary phase particles were adjusted by controlling the annealing temperature. Thermodynamic calculations were performed to identify the fractions of the secondary phase particles. The finite element method was conducted to confirm the localized deformation around the secondary phase particles considering 3-dimensional microstructure. The results suggest that the total fraction of the secondary phase particles affected the localized deformation around the particles and micro-crack propagation process during a tensile test.</P>
Role of reactive thrombocytosis after primary cytoreductive surgery in advanced ovarian cancer
( Seung Hun Baek ),( Joseph J. Noh ),( Jung In Shim ),( Jun Hyeok Kang ),( Soo Young Jeong ),( Chel Hun Choi ),( Tae-joong Kim ),( Jeong-won Lee ),( Byoung-gie Kim ),( Duk-soo Bae ),( Yoo-young Lee ) 대한산부인과학회 2020 대한산부인과학회 학술대회 Vol.106 No.-
Objective: Surgery induced thrombocytosis occurs frequently in various disease. We investigated the incidence of reactive thrombocytosis after maximal cytoreductive surgery in epithelial ovarian cancer and its role on survival. Methods: An electronic chart review was performed of advanced epithelial ovarian cancer patients who had primary cytoreductive surgery from January 1, 2012, and December 31, 2017. Besides from known clinical prognostic factors, serum platelet counts at various time points including before surgery, during peri-operative period, and on each cycle of adjuvant chemotherapy were collected. Results: 474 patients were eligible for the analysis. Median age was 55 years (18 -88) and pretreatment CA 125 was 1519.2 U/mL (5.5-16719). 401 patients (84.6%) were FIGO Stage III and serous histology was most common (405 patients, 85.4%). 79 patients (22.6%) had splenectomy and optimal cytoreduction (residual < 1cm) was achieved at 326 patients (68.8%). Thrombocytosis was observed in 273 patients (57.6%) patients in the entire cohort. Especially, higher platelet counts were observed in patients with splenectomy compared without splenectomy (e.g. on post-operative day 12, p<0.001). Subgroup of patients who still had thrombocytosis during adjuvant chemotherapy showed poorer survivals than the others. In particular, thrombocytosis on 5th cycle of adjuvant chemotherapy showed most significant impact on overall survival (HR; 1.871, 95%CI; 1.034-3.386, p=0.038) among various time points in multivariate analysis. In a logistic regression model, splenectomy (p<0.001) and optimal cytoreduction (p=0.025) significantly attributed to thrombocytosis on 5th cycle. Conclusion: Our findings suggest that reactive thrombocytosis after primary cytoreductive surgery is associated with poor survival in advanced ovarian cancer, particularly when splenectomy was performed and thrombocytosis was observed during adjuvant chemotherapy. New approaches to increase oncological outcomes are needed for this subgroup of patients.
Long-term stability study of graphene-passivated black phosphorus under air exposure
Jiho Kim,Seung Kwan Baek,Keun-Soo Kim,Young Jun Chang,E.J. Choi 한국물리학회 2016 Current Applied Physics Vol.16 No.2
We use the graphene as a passivation layer to protect the black phosphorus from chemical reaction with air. Flakes of the black phosphorus crystal are covered by N ¼ 1, 2, and 3 layers of CVD graphene and the Raman phonon modes are measured after the samples are exposed to air. For the double and triple layer passivation (N ¼ 2,3) the Raman phonon peaks are maintained as long as ~100 h (4 days) before the phonon intensity is reduced to 90% of the initial strength, I/I0 ¼ 0.9, demonstrating that the black phosphorus is strongly protected in contrast to the rapid degradation of the bare and single-layer covered black phosphorus. The long term stability achieved by multi-layer graphene passivation makes it possible to perform various electronic and optical experiments aimed for device application of this direct-gap van der Waals semiconductor with high electronic and thermal mobility under ambient environment.