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UV radiation pretreatment for reverse osmosis (RO) process in ultrapure water (UPW) production
Jin, Yongxun,Lee, Hyunkyung,Zhan, Min,Hong, Seungkwan Elsevier 2018 Desalination Vol.439 No.-
<P><B>Abstract</B></P> <P>In ultrapure water (UPW) production, ultraviolet (UV) radiation is an effective process for reducing microorganisms and organic matter. An increasing trend of reusing the spent UPW further encourages the adoption of UV at the upstream of reverse osmosis (RO) to mitigate membrane fouling and to enhance water quality. In this study, UV technology, both low and medium pressure lamps, was assessed for RO pretreatment in UPW production. The fouling potential of problematic pollutants (e.g., silica and IPA) was evaluated pre and post UV treatment based on fouling index under constant flux mode. We found that the rejection rate of IPA was enhanced up to 80% and thus reduced the organic fouling potential in RO. On the contrary, for inorganic nano-particle such as silica, a significant increase in fouling potential after UV exposure was observed. Zeta and small angle X-ray scattering analysis implied that this fouling potential transition was derived from silica particle agglomeration under UV radiation. The RO fouling tests corroborated findings from fouling index measurements, showing severe flux decline after UV radiation. This research provides new insight for UPW production design by revealing the influence of UV on inorganic and organic pollutants during the reclamation of spent UPW.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UV radiation was evaluated as pretreatment for RO in reclamation of spent UPW. </LI> <LI> Fouling in RO was simulated by fouling index newly developed for UPW process. </LI> <LI> UV treatment effectively degraded low-molecular weight organic matter (IPA). </LI> <LI> UV dose is a dominant factor which controls the rise of silica fouling. </LI> <LI> Increased silica fouling was manifested by aggregation under UV exposure. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
진흉쉰(Jin, Yongxun),김상규(Kim, Sangkyu) 인제대학교 디자인연구소 2017 Journal of Integrated Design Research (JIDR) Vol.16 No.3
연구배경: 일상생활에서 일부 소비자들이 비이성적인 의사결정을 하며 미신적 의미가 부여된 제품을 더 선호하는 경향을 종종 볼 수 있다. 이러한 행위 현상은 제품디자인이 미신이라는 비이성적 요소와 관계가 있음을 보여주는 증거가 된다. 그럼에도 불구하고 현재 미신과 관련된 실증 연구, 특히 미신과 제품디자인 간의 관련 연구는 아직 미흡한 실정이다. 연구방법: 기본적으로 문헌조사와 선행연구검토를 바탕으로 구체적인 사례 조사 및 분석의 방법을 적용하였다. 연구결과: 여러 사례를 보면 사실상 일상생활에서 뿐만 아니라 디자인 측면에서도 미신이 영향을 미치고 있음을 알 수 있었다. 이는 논리적이지 않은 것도 디자인에 중요한 요인이 될 수 있음을 뜻한다. 결론: 본 연구는 소비자의 미신적 신념이 제품 태도에 영향을 미치는가를 살펴보았다. 소비자의 미신적 신념이 제품의 선택에 많은 영향을 미친 것으로 나타났으며 따라서 디자이너가 이러한 소비자의 행위를 중요하게 고려할 필요가 있다. 또한 디자인 과정에서 이러한 비이성적인 방법을 적용할 수 있고 제품디자인의 결과에서도 좋은 효과를 거둘 수 있다. Background: In daily lives, through observing customers" behaviors, we can find out some irrational decision-making behaviors. Customers will particularly have much greater buying desires towards the commodities which involve with superstition. This indicates that there ae some connections between industrial design and irrational superstitious behavior. what’s more, the research about the relation between industrial design and superstition is still deficient and imperfect. Methods: Basically, specific case studies and method of analysis were applied based on documentary survey and preceding research. Result: Through analyzing all kinds of cases, it turns out that the influence of superstition not only exists in the daily lives but also exists in the industrial design and can be a composing element in designing. Conclusion: The research studies the customers’ attitudes towards superstitious commodities only to find that superstition plays a certain part in customers’ final decisions. Therefore, during the designing process we should pay more attention to this kind of behavior and use superstition as an entry point in order to make the final design of the product more attractive and prominent.
Understanding possible underlying mechanism in declining germicidal efficiency of UV-LED reactor
Lee, Hyunkyung,Jin, Yongxun,Hong, Seungkwan Elsevier 2018 Journal of photochemistry and photobiology. B, Bio Vol.185 No.-
<P><B>Abstract</B></P> <P>Since ultraviolet light emitting diodes (UV-LEDs) have emerged as an alternative light source for UV disinfection systems, enhancement of reactor performance is a demanding challenge to promote its practical application in water treatment process. This study explored the underlying mechanism of the inefficiency observed in flow-through mode UV disinfection tests to improve the light utilization of UV-LED applications. In particular, the disinfection performance of UV-LED reactors was evaluated using two different flow channel types, reservoir and pathway systems, in order to elucidate the impact of physical circumstances on germicidal efficiency as the light profile was adjusted. Overall, a significant reduction in germicidal efficiency was observed when exposure time was prolonged or a mixing chamber was integrated. Zeta analysis revealed that the repulsion rate between microorganisms decreased with UV fluence transfer, and that change might cause the shielding effect of UV delivery to target microorganisms. In line with the above findings, the reduction in efficiency intensified when opportunities for microbial collision increased. Thus, UV induced microbial aggregation was implicated as being a disinfection hindering factor, exerting its effect through uneven UV illumination. Ultimately, the results refuted the prevailing belief that UV has a cumulative effect. We found that the reservoir system achieved worse performance than the pathway system despite it providing 15 times higher UV fluence: the differences in germicidal efficiency were 1-log, 1.4-log and 1.7-log in the cases of <I>P.aeruginosa</I>, <I>E.coli</I> and <I>S.aureus</I>, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The reduction of germicidal efficiency in UV-LEDs was fundamentally examined. </LI> <LI> UV changed the dispersal state of microorganisms, inducing microbial aggregation. </LI> <LI> Microbial aggregation resulted in lower performance by shielding UV delivery. </LI> <LI> The risk of a shielding effect increases with exposure time in UV disinfection. </LI> <LI> Performance of a UV-LED reactor was enhanced by overcoming the shielding effect. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>
Some results on total colorings of planar graphs
Jianfeng Hou,Guizhen Liu,Yongxun Xin,Mei Lan 한국전산응용수학회 2008 Journal of applied mathematics & informatics Vol.26 No.3-4
Let G be a planar graph. It is proved that if G does not contain a k-cycle with a chord for some k ∈ {4, 5, 6}, then G is total-(△(G) + 2)-colorable.