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Shinyun Park,Eunmok Yang,Hosik Park,Heechul Choi 대한환경공학회 2020 Environmental Engineering Research Vol.25 No.5
Halloysite nanotubes (HNTs) were functionalized using 3-aminopropyltriethoxysilane (APTES) and incorporated into polyethersulfone (PES) membranes to improve the hydrophilicity of the membranes as well as the interfacial interaction between HNTs and the polymer matrix. The intrinsic properties, permeability, and selectivity of the prepared membranes were analyzed to evaluate the membrane performance. In addition, humic acid (HA) fouling experiments were conducted to measure the antifouling properties of the fabricated membranes. As HNTs and functionalized HNTs (f-HNTs) contents are increased, hydrophilicity and mechanical strength were enhanced, and membranes with f-HNTs showed further improved performance. The pure water flux of membranes with 2% HNTs and f-HNT was 7.5 times higher than that of a pristine PES membrane without a trade-off relation between the water flux and HA rejection. The membranes with f-HNTs showed the highest antifouling properties compared to membranes with HNTs because enhanced hydrophilicity played a key role in preventing accumulation of HA.
Yanar, Numan,Son, Moon,Yang, Eunmok,Kim, Yeji,Park, Hosik,Nam, Seung-Eun,Choi, Heechul Elsevier 2018 CHEMOSPHERE - Vol.202 No.-
<P><B>Abstract</B></P> <P>Recently, feed spacer research for improving the performance of a membrane module has adopted three-dimensional (3D) printing technology. This study aims to improve the performance of membrane feed spacers by using various materials and incorporating 3D printing. The samples were fabricated after modeling with 3D computer-aided design (CAD) software to investigate the mechanical strength, water flux, reverse solute flux, and fouling performances. This research was performed using acrylonitrile butadiene styrene (ABS), polypropylene (PP), and natural polylactic acid (PLA) as printing material, and the spacer model was produced using a diamond-shaped feed spacer, with a commercially available product as a reference. The 3D printed samples were initially compared in terms of size and precision with the 3D CAD model, and deviations were observed between the products and the CAD model. Then, the spacers were tested in terms of mechanical strength, water flux, reverse solute flux, and fouling (alginate-based waste water was used as a model foulant). Although there was not much difference among the samples regarding the water flux, better performances than the commercial product were obtained for reverse solute flux and fouling resistance. When comparing the prominent performance of natural PLA with the commercial product, PLA was found to have approximately 10% less fouling (based on foulant volume per unit area and root mean square roughness values), although it showed similar water flux. Thus, another approach has been introduced for using bio-degradable materials for membrane spacers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> By utilizing various materials, 3D printed membrane feed spacers were successfully fabricated. </LI> <LI> Better performances than commercial products were obtained (for mechanical strength, water flux, reverse solute flux, and fouling). </LI> <LI> The effects of spacers' surface roughness on water flux and fouling were investigated. </LI> <LI> Biopolymer polylactic acid was used as a spacer material; it exhibited a very high performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
성열욱,이현규,양은목,Sung, Yeoul Ouk,Lee, Hyun Kyu,Yang, Eunmok The Society of Digital Policy and Management 2021 디지털융복합연구 Vol.19 No.10
X와 Y사이의 퍼지 관계를 곱집합 X × Y의 퍼지 부분집합으로 Zadeh에 의해 처음으로 소개된 이후 퍼지집합에 대한 개념은 자연과학 및 컴퓨터과학에서 많은 연구성과가 이루어져 왔다. 그 결과 Muralli와 Nemitz는 동치관계 및 함수와 관련하여 퍼지관계를 연구하였고, Ounalli와 Jaoua는 중요한 수학적 도구로서 퍼지 다이펑션날 관계를 정의하여 소프트디자인과 데이터베이스 이론에서 중요한 역할을 하는 것으로 증명되었으며, 또한 프로그램 표식과 프로그램 정확도를 정의하는데 유용한 것으로 밝혀졌다. 본 논문에서는 한 집합 위에 퍼지 디터미니스틱 관계를 정의하여 퍼지 디터미니스틱 관계를 레벨 부분집합으로 특성화 하였고, 퍼지 디터미니스틱 관계와 관련하여 일부 성질을 증명하였다. 특히, 퍼지 디터미니스틱 관계와 퍼지 함수가 동치임을, 퍼지 함수가 퍼지 다이펑션날 관계가 동치임을 증명하였다. A fuzzy relation between X and Y as fuzzy subset of X × Y was proposed by Zadeh. Subsequently, several researchers have applied the notion of fuzzy subsets to various branches of mathematics and computer sciences. Murali an Nemitz have studied fuzzy relations connected with fuzzy equivalence relations and fuzzy functions. Ounalli and Jaoua defined a fuzzy difunctional relation on a set. difunctional relations are versatile mathematical tool, which can be used in software design and in database theory. Their work have revealed the usefulness of difunctional relations in program specification and in defining program correctness. The main goal of this paper is to define a fuzzy deterministic relation on a set, characterize the fuzzy deterministic relation as its level subsets and investigate some properties in connection with fuzzy deterministic relation. In particular we prove that a fuzzy relation R is fuzzy deterministic iff R is a fuzzy function.