PLC Program 검증을 위한 심볼 표준화에 관한 연구

홍상현,방성문,왕지남 대한산업공학회 2012 대한산업공학회 추계학술대회논문집 Vol.2012 No.11

생산 능률의 증진과 원가 절감, 품질 향상, 업무 운영을 확실하게 할 수 있는 효과를 가져옴으로 여러 산업의 다양한 곳에서 표준화가 이루어 지고 있다. 자동차 산업의 생산시스템의 경우도 차종에 따른 디자인 옵션 전자장치의 추가 및 변경이 잦아짐에 따라, 주어진 시간 내에서의 시스템 안정화가 이슈가 되고 있다. 이를 위해 생산시스템을 제어하는 PLC 프로그램을 검증하여 발생 가능한 오류를 사전에 제거하는 작업이 필요하다. 이러한 검증 작업을 위한 방법론으로 PLC CODE 표준 모델 적용과 심벌의 표준화이다. 라인의 각 공정 설비 기능에 부합되는 PLC CODE의 표준 모델 FB(FUNCTION BLOCK)의 항목을 분류하여 PLC 프로그램 설계에 적용한다. 심벌 표준화를 위해서는 심벌의 용어 표준화와 심벌에 사용되는 용어의 순서를 정하는 표준화가 필요하다. PLC CODE 표준 모델과 심벌 표준화 적용을 통하여 프로그램 설계 기간 단축, 표준화된 심벌을 사용하여 PLC 프로그램 검증 기간 단축, 고 품질의 PLC프로그램 완성도를 기대할 수 있다. 이는 궁극적으로 생산까지의 기간과 단축과 비용 절감의 효과를 가져 오게 된다.

다낭성 신종으로 인한 신부전 환자에서 동시적 신장 절제 및 신장이식 후 발생한 지속적 저혈압 -증례 보고-

홍상현,허재원,이재민 대한마취통증의학회 2015 Anesthesia and pain medicine Vol.10 No.4

Patients with autosomal dominant polycystic kidney disease have significant morbidity due to large kidney size. Surgical extirpation of polycystic kidneys is frequently necessary to treat the morbidity or to obtain intraabdominal space for a graft kidney. Simultaneous bilateral nephrectomy and kidney transplantation are performed in many transplant centers to avoid the complications associated with anephric states such as anemia requiring blood transfusion, osteodystrophy, fluid overload, hyperkalemia, and congestive heart failure. However, the risk of postoperative complications after combined bilateral nephrectomy with kidney transplantation is relatively high, especially for cases in which the polycystic kidneys are huge. Here, we report two cases of severe and persistent hypotension during and after combined surgery which may have been caused by adrenal insufficiency or by sympathetic denervation and splanchnic vasculature decompression after the removal of huge polycystic kidneys.

Stablility increased alginate gel prepared by liknkage exchange

홍상현,이해신 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0

Calcium-alginate hydrogels have received great attentions as scaffolding material because they have low toxicity, good mechanical properties and easily form hydrogel via ionic interaction. However, the major drawback to these systems is rapid dissipation of mechanical properties and degradation by loss of cations. Herein, we developed catechol conjugated alginate hydrogel through EDC/NHS coupling. The mechanical properties of hydrogel were kinetically controlled by two phases of cross-linking. This alginate-catechol hydrogel showed high stability over months in physiological condition even after calcium ions dissociated as time passed and elastic modulus (G’) was continuously maintained, which cannot be achieved in ionic hydrogels. As potential application, alginate hydrogel was manufactured in 3-D scaffold and cytotoxicity test was also performed. This hydrogel may enhance the potential for biomedical applications such as tissue engineering.

Effect of charge on in vivo adhesion stability of catechol-conjugated polysaccharides

홍상현,류지현,이해신 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.79 No.-

Mussel-inspired adhesive materials have received much attention for biomedical applications primarilybecause of their underwater/tissue adhesive properties. However, so far, no comparative study focusingon effect of charge differences (i.e., positive vs. negative) in the presence of conjugated catechols has beenconducted. In this study, we investigate the physicochemical characteristics and in vitro/in vivo tissueadhesive properties of hydrogels that use anionic (i.e., hyaluronic acid) and cationic (i.e. chitosan)catechol-conjugated polysaccharides. Fe(III) is utilized to effectively prepare both hydrogels. Hyaluronicacid-catechol (HA-C) hydrogels are immediately formed by iron-catechol coordination bonds, whilechitosan-catechol (CHI-C) hydrogel is formed by both iron-catechol coordination and catechol-aminecovalent reactions. The gelation time and in vitro adhesiveness are similar for both CHI-C and HA-Chydrogels. Differences are found in that the CHI-C hydrogels showed enhanced water-resistance andlong-lasting adhesion in vivo. It is noteworthy to mention that the cationic nature of mussel adhesiveproteins due to lysine and histidine residues in the pads of Mytilus edulis is known to be an importantcontributor to underwater adhesion. Thus, this comparative study provides significant insight for thedesign of effective mussel-inspired adhesive materials.

HVPE 방법에 의해 r-plane 사파이어 기판 위의 선택 성장된 GaN/AlGaN 이종 접합구조의 특성

홍상현,전헌수,한영훈,김은주,이아름,김경화,황선령,하홍주,안형수,양민,Hong, S.H.,Jeon, H.S.,Han, Y.H.,Kim, E.J.,Lee, A.R.,Kim, K.H.,Hwang, S.L.,Ha, H.,Ahn, H.S.,Yang, M. 한국결정성장학회 2009 한국결정성장학회지 Vol.19 No.1

본 논문에서는 혼합소스(mixed-source) HVPE(hydride vapor phase epitaxy)방법으로 선택성장(SAC: selective area growth) GaN/AlGaN 이종접합구조의 발광다이오드를 r-plane 사파이어 기판 위에 제작하였다. SAG-GaN/AlGaN DH(double heterostructure)는 고온 GaN 버퍼층, Te 도핑된 AlGaN n-클래딩층. Gan 활성층. Mg 도핑된 AlGaN p-클래딩층. Mg 도핑된 GaN p-캡층으로 구성되어있다. GaN/AlGaN 이종접합구조의 발광다이오드의 특성을 알아보기 위해 SEM을 통한 구조적 분석과 전류-전압 측정(I-V: current-voltage measurement), 전류-광출력(EL: electroluminescence) 측정을 통하여 전기적, 광학적 특성을 평가하였다. In this paper, a selective area growth (SAG) of a GaN/AlGaN double heterostructure (DH) has been performed on r-plane sapphire substrate by using the mixed-source hydride vapor phase epitaxy (HVPE) with multi-sliding boat system. The SAG-GaN/AlGaN DH consists of GaN buffer layer, Te-doped AlGaN n-cladding layer, GaN active layer, Mg-doped AlGaN p-cladding layer, and Mg-doped GaN p-capping layer. The electroluminescence (EL) characteristics show an emission peak of wavelength, 439 nm with a full width at half maximum (FWHM) of approximately 0.64 eV at 20 mA. The I-V measurements show that the turn-on voltage of the SAG-GaN/AlGaN DH is 3.4 V at room temperature. We found that the mixed-source HVPE method with a multi-sliding boat system was one of promising growth methods for III-Nitride LEDs.

Mussel-inspired surface functionalization by tethering of aldehyde-containing molecule

홍상현,이해신 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

Polydopamine (pDA) coating has been issued in the past decade due to its unique material-independent surface modification property. Deposited pDA layers have been applied to various fields because it can be functionalized through simple co-deposition of materials and dopamine. However, this reaction is limited to amine- and thiol-containing molecules, and functionalization with aldehyde has been rarely attempted. Here, we develop a surface functionalization strategy by dopamine-aldehyde coupling, and modified substrates successfully demonstrated anti-fouling, hydrophobic, protein-affinity properties.

Single Component Hydrogel Exhibiting Stretchable, Self-healing,and Mutifunctional Properties Simultaneously

홍상현,이해신 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

For the increasing demand of soft materials with wide range of applications, hydrogels have been developed exhibiting variety of functions. In general, most hydrogels have been designed by multiple component to achieve some functionalities. Multi-conponent systems often requires tremendous labors during preperation process and accompany undesirable reactions that can be avoidable in single component hydrogel system. Here, we developed single component hydrogel, alginate-boronic acid hydrogel, that can exhibit unprecedented multi-functionalities simultaneously such as high stretchable, self-healing, shear-thinning, pH- and glucose-sensitivities, adhesive, and re-shaping properties. Multi-functionalities of alginate-BA hydrogel is resulted from the reversible inter-, intra-molecular interactions by dynamic equilibrium of boronic acid-diol complexation and dissociation. These findings suggest that this novel hydrogel have potentials for use in wide range of biomedical applications.

Ultrafast sprayable polydopamine surface modifications

홍상현,이해신 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

Controlled synthesis of alginate hydrogel via boronic acid and cis-diol interactions

홍상현,이해신 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

Hydrogels have been used for many applications due to its unique and desirable properties. And those characteristics and applications of the gels are closely related to their preparation methods. In this study, we introduced boronic acid (BA) into alginate backbone for specific binding between BA and diol group in alginate and successfully prepared hydrogel by its own component without adding any other cross-linkers. The hydrogel showed high sensitivity to pH change due to the pH responsibility of the BA-diol interactions. Furthermore alginate-BA gel prepared under specific conditions showed interesting mechanical properties such as sol-gel transition, adhesiveness, self-healing, re-shaping, superior elongation. We expect that these excellent mechanical properties and specific binding with diol can be used for biomedical applications.

Stability increase of Ca²⁺-alginate hydrogels by spontaneous ionic-to-covalent bond exchange

홍상현,이해신 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

Alginate is a linear polysaccharide extracted from brown algae and composed of homopolymeric blocks of (1-4)-linked β-D-mannuronic acid (M) and α-L-guluronic acid (G). The most representative features of alginates are the stiffnesses of their polymer chains and their affinities to various transition metal cations, such as Cd²⁺, Ni²⁺, or Mn²⁺, which could be exploited for metal removal in environmental science and engineering. Recently, applications have been expanded to energy storage devices. For example, alginate is used as a silicon anode binder in Li-ion batteries due to the stiffness of the alginate backbone. In addition to environmental sciences and energy storage technologies, the most well-known research field utilizing alginate has been biomaterial sciences. The prompt formation of alginate gels in the presence of calcium ions in aqueous solutions (known as Ca²⁺-alginate gel) has been a useful method of encapsulating and then releasing various macromolecular pharmaceuticals. An early example is the encapsulation of islets to release insulin upon the infusion of glucose for treating diabetes. Additionally, alginate gels are used for local delivery of incorporated vascular endothelial growth factor (VEGF) to enhance angiogenesis in peripheral tissues. Despite the widespread uses, the major drawback of Ca²⁺-alginate gels is rapid gel dissolution due to ionic bond dissociation between the encapsulated Ca²⁺ ions and the carboxylic acid (R-COO-) groups along alginate backbones. This issue prevents the widespread use of Ca²⁺-alginate hydrogels for drug delivery or tissue engineering scaffolds. Methods to overcome this gel dissolution have been developed mostly using cationic polymer coatings. The coatings performed with poly L-lysine, chitosan, or poly(ethylenimine) on hydrogel surfaces showed increased physical stabilities, but nonetheless, the dissociation of the coated polymers is unavoidable, resulting in problems for long-term stability. Alternatively, the formation of covalent bonds via carbodiimide conjugation or reductive amination chemistries increases the physical stability. However, these approaches are generally not compatible with in situ encapsulations of cells or proteins due to the presence of coupling agents. Thus, we hypothesized that combining these two approaches (ionic and covalent linkages) might provide a new method to prepare alginate hydrogels. Our new approach uses ionic couplings for cell encapsulation initially and later in time the covalent bonds are formed, which gradually replace the ionic bonds, thus increasing the physical stability of the alginate gel. We called this alginate gel ‘STAPLE’, an abbreviation for Stable Alginate gel Prepared via Linkage Exchange from ionic to covalent bonds. The key chemistry in STAPLE is the ionic to covalent bond transitions, where the catechol moieties tethered along alginate chains are slowly oxidized to catecholquinone. The catecholquinone mediated crosslinking kinetics are well matched with the kinetics of Ca²⁺ dissociation at pH 7.4 and 37°C. Thus, the original physicochemical integrity of the hydrogel is preserved even after the Ca²⁺ dissociation. This novel method to prepare alginate hydrogels may increase the potential utility in a variety of biomedical applications.