Dispersion and reaggregation of nanoparticles in the polypropylene copolymer foamed by supercritical carbon dioxide

Oh, Kyunghwan,Seo, Youngwook P.,Hong, Soon Man,Takahara, Atsushi,Lee, Kyoung Hwan,Seo, Yongsok The Royal Society of Chemistry 2013 Physical chemistry chemical physics Vol.15 No.26

<P>For the preparation of nanocomposites, we conducted environmentally benign foaming processing on polypropylene (PP) copolymer/clay nanocomposites <I>via</I> a batch process in an autoclave. We investigated the dispersion and the exfoliation of the nanoclay particles. Full exfoliation was achieved by the foamability of the matrix PP copolymer using supercritical carbon dioxide (sc CO<SUB>2</SUB>) and subcritical carbon dioxide (sub CO<SUB>2</SUB>). More and smaller cells were observed when the clay was blended as heterogeneous nuclei and sc CO<SUB>2</SUB> was used. Small angle X-ray scattering showed that highly dispersed states (exfoliation) of the clay particles were obtained by the foaming process. Since the clay particles provided more nucleating sites for the foaming of the polymer, a well dispersed (or fully exfoliated) nanocomposite exhibited a higher cell density and a smaller cell size at the same clay particle concentration. Expansion of the adsorbed CO<SUB>2</SUB> facilitated the exfoliation of the clay platelets; thus, sc CO<SUB>2</SUB> at lower temperature was more efficient for uniform foaming-cell production. Fully dispersed clay platelets were, however, re-aggregated when subjected to a further melting processing. The reprocessed nanocomposites still had some exfoliated platelets as well as some aggregated intercalates. The dual role of the nanoclay particles as foaming nucleus and a crystallization nucleus was confirmed by cell growth observation and nonisothermal crystallization kinetics analysis. A low foaming temperature and a high saturation pressure were more favorable for obtaining a uniform foam. The PP copolymer was found to be foamed more easily than polypropylene. A small amount of other olefin moieties in the backbone of the polymer facilitated better foamability than the neat polypropylene.</P> <P>Graphic Abstract</P><P>Polypropylene copolymer nanocomposite was more easily foamed than polypropylene by supercritical CO<SUB>2</SUB>, the expansion of which helped the exfoliation of clay platelets. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3cp51068a'> </P>

Medication Adherence in Korean Patients with Inflammatory Bowel Disease and Its Associated Factors

Kyunghwan Oh,Eun Ja Kwon,Jeong Hye Kim,Kyuwon Kim,Jae Yong Lee,Hee Seung Hong,Seung Wook Hong,Jin Hwa Park,Sung Wook Hwang,Dong-Hoon Yang,Byong Duk Ye,Jeong-Sik Byeon,Seung-Jae Myung,Suk-Kyun Yang,Jeo 이화여자대학교 의과학연구소 2022 EMJ (Ewha medical journal) Vol.45 No.2

Objectives: It is important that inflammatory bowel disease (IBD) patients adhere to their prescribed medication regimens to avoid the repeat exacerbations, complications, or surgeries associated with this disorder. However, there are few studies on medication adherence in patients with IBD, especially in Asian populations. So, we analyzed the factors associated with medication adherence in Korean IBD patients. Methods: Patients who had been diagnosed with Crohn’s disease (CD) or ulcerative colitis (UC) more than 6 months previously and receiving oral medications for IBD were enrolled. Medication adherence was measured using the Medical Adherence Reporting Scale (MARS-5), a self-reported medication adherence measurement tool. Results: Among 207 patients in the final study population, 125 (60.4%) had CD and 134 (64.7%) were men. The mean age was 39.63 years (SD, 13.16 years) and the mean disease duration was 10.09 years (SD, 6.33 years). The mean medication adherence score was 22.46 (SD, 2.86) out of 25, and 181 (87.4%) patients had score of 20 or higher. In multiple linear regression analysis, self-efficacy (β=0.341, P<0.001) and ≥3 dosing per day (β=–0.192 P=0.016) were revealed to be significant factors associated with medication adherence. Additionally, there was a positive correlation between self-efficacy and medication adherence (r=0.312, P<0.001). However, disease related knowledge, depression, and anxiety were not significantly associated with medication adherence. Conclusion: To improve medication adherence among patients with IBD, a reduction in the number of doses per day and an improved self-efficacy will be helpful.

Critic on the Relationship between Faith and Reason Suggested by Thomas Aquinas and Christian Educational Implications

Oh Kyunghwan ( 오경환 ) 개혁신학회 2021 개혁논총 Vol.56 No.-

This paper articulates the claims of the medieval theologian Thomas Aquinas who attempted to integrate the relationship between faith and reason within Christian theology. Aquinas failed to synthesize faith and reason biblically because he failed to examine thoroughly the relationship as it relates to biblical anthropology. He refused to acknowledge man’s total depravity, incompetence, and epistemological flaws. This paper discerns the correlation between faith and reason from a biblical perspective by examining general revelation and special revelation and the implications and significances of faith and reason to Christian education. This study concludes that Aquinas’s attempts to integrate the relationship between faith and reason are not based on biblical anthropology and epistemology as they prove that only the Holy Spirit leads fallen human beings to the true living God. 본 논문은 기독교 신학 내에서 신앙과 이성의 문제를 통합하려고 시도했던 중세의 신학자 토마스 아퀴나스의 주장에 대해 연구한다. 아퀴나스는 신앙과 이성을 종합하려고 했지만 인간의 전적 타락과 무능 및 인간의 성경적 인간론을 거부함으로 이 둘의 관계를 철저하게 규명하는 데 실패했다. 이 연구는 신앙과 이성의 문제를 기독교적 관점과 기독교적 세계관으로 다룰 뿐 아니라, 기독교 교육의 시사점과 중요성 및 함의에 대해 다루며 동시에 성경적 인간의 이해가 무엇인지를 일반 계시와 특별 계시를 통해 연구한다. 결론적으로 본 연구는 성경적 인간론 및 인식론에 기반하지 못한 아퀴나스의 신앙과 이성의 관계를 통합한 시도에 대해 비평 및 고찰을 시도하며, 오직 성령 하나님만이 무능하고 타락한 인간을 살아계신 진리의 하나님께로 인도한다는 것을 확증한다.

Development of microoptical waveguide on microactuating platform technologies for reconfigurable optical networking

Oh, Kyunghwan,Shin, W.,Jeong, Y.S.,Lee, J.W. IEEE 2005 Journal of lightwave technology Vol.23 No.2

This paper reports on new hybrid optomechanical technology for reconfigurable optical networking applications. Unique and versatile functions in the technology were provided by micrometer-scale fused-taper waveguides mounted on microelectromechanical actuating platforms. The proposed technology can endow new degrees of freedom to control spectral response and port-to-port output power of the throughput of multiport fiber-fused-taper devices. Applications in a reconfigurable optical switch, an interband router, and a high-power optical attenuator for optical networking are discussed.

Waveguide dispersion of clad modes and its effects on the spectra of long period fiber grating

Kyunghwan Oh 한국통신학회 1999 한국통신학회 광전자공학 학술회의 Vol.1999 No.5

Bronchoesophageal fistula in a patient with Crohn’s disease receiving anti-tumor necrosis factor therapy

Kyunghwan Oh,Kee Don Choi,Hyeong Ryul Kim,Tae Sun Shim,Byong Duk Ye,Suk-Kyun Yang,Sang Hyoung Park 대한소화기내시경학회 2023 Clinical Endoscopy Vol.56 No.2

Tuberculosis is an adverse event in patients with Crohn’s disease receiving anti-tumor necrosis factor (TNF) therapy. However, tuberculosis presenting as a bronchoesophageal fistula (BEF) is rare. We report a case of tuberculosis and BEF in a patient with Crohn’s disease who received anti-TNF therapy. A 33-year-old Korean woman developed fever and cough 2 months after initiation of anti-TNF therapy. And the symptoms persisted for 1 months, so she visited the emergency room. Chest computed tomography was performed upon visiting the emergency room, which showed BEF with aspiration pneumonia. Esophagogastroduodenoscopy with biopsy and endobronchial ultrasound with transbronchial needle aspiration confirmed that the cause of BEF was tuberculosis. Anti-tuberculosis medications were administered, and esophageal stent insertion through endoscopy was performed to manage the BEF. However, the patient’s condition did not improve; therefore, fistulectomy with primary closure was performed. After fistulectomy, the anastomosis site healing was delayed due to severe inflammation, a second esophageal stent and gastrostomy tube were inserted. Nine months after the diagnosis, the fistula disappeared without recurrence, and the esophageal stent and gastrostomy tube were removed.

Index guiding air silica holey fibers, their theoretical backgrounds, and applications

Kyunghwan Oh(오경환) 한국통신학회 2009 한국통신학회 기타 간행물 Vol.2009 No.12

근대 사회과학의 아포리아 : 사회과학의 ‘인간’ 개념을 중심으로

Kyunghwan Oh 문화사학회 2011 역사와 문화 Vol.22 No.-

Modernity, in Kant’s and Foucault’s understanding, takes the doublet of a man as a central feature. Stemming from Humean skepticism and the ensuing epistemological crisis, Kant posited the Man in a perpetual oscillation between transcendence and empirical ‘reality.’ The history of social science from Comte and Marx to Weber and Durkheim is continuous reformulation of Kant’s epistemology. Comte and Marx tried to evade the epistemological problem of doublet by recasting human phenomena through specific nomos: Comte by projecting onto them transcendental humanity that is transhistorically applicable; and Marx by reducing them to empirical reality organized by specific nomos. Though Both succeeded to a certain extent in creating viable and practicable social science, they created a whole new problem of normative science. Rejecting such nomology, Weber and Durkheim tried to base social science on a different epistemological percepts by recasting the object of social science. Durkheim re-imagined human beings in proto-structuralist postulation, hitting a delicate balance. Weber, on the other hand, returned to the idea of civilization, while taking great cautions not to project evolutionary bias. Still, both of them could not completely escape Eurocentric underpinnings, because their recasting of men still followed the basic presupposition of modernity, which is in turn product of the European historical experiences.

Novel hollow optical fibers and their applications in photonic devices for optical communications

Oh, Kyunghwan,Choi, S.,Jung, Yongmin,Lee, J.W. IEEE 2005 Journal of lightwave technology Vol.23 No.2

Novel photonic devices based on a new type of waveguide, hollow optical fibers (HOF), are described. Utilizing unique three layered structure of HOF, the central air hole, germanosilicate ring core, and silica cladding along with its adiabatic mode transformation capability we demonstrated versatile applications in short-haul, long-haul optical communications, and tunable wavelength selective devices. Detailed design parameters, fabrication arts of the fibers, and operation principles of the devices are discussed.

Design of dispersion controlled optical fibers for wavelength division multiplexed optical communication system

Kyunghwan Oh,백운출,정영주,송계휴 에스케이텔레콤 (주) 1998 Telecommunications Review Vol.8 No.1

In a large capacity wavelength division multiplexed system, the dispersion in optical fiber is one of critical parameters that determine the efficiency of nonlinear interactions as well as the transmission distance. In this study two types of dispersion controlled fibers were rigorously analyzed. For dual mode fiber that supports both the fundamental mode LP01 and the first excited mode LP11, exact eigen values of the vectorial Maxwell’s equations were numerically obtained. The dispersion characteristics have been rigorously analyzed for various index profiles including the effects of material dispersion of cladding and core for the applications in dispersion compensation. A new non-zero dispersion fiber design has been developed to optimize both linear and nonlinear distortions in the 1.5μm EDFA gain band to improve the performance of wavelength division multiplexed system. Index terms-optical fiber, dispersion, waveguide design, nonlinearity in optical fiber