Dropwise gelation-dehydration kinetics during drop-on-demand printing of hydrogel-based materials

Han, Bumsoo,Yun, Gyu Young,Boley, J. William,Kim, Samuel Haidong,Hwang, Jun Young,Chiu, George T.-C.,Park, Kinam Elsevier 2016 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.97 No.-

<P><B>Abstract</B></P> <P>The present study aims to characterize and understand the dropwise gelation-dehydration phenomena during drop-on-demand (DOD) printing of hydrogel-based soft materials. Functional soft materials have broader impacts on many medical and engineering applications, but constructing soft materials into three-dimensional (3D) configuration with spatially varying properties is still extremely challenging. In order to establish a mechanistic understanding, a hypothesis was postulated that the porosity of hydrogel printed is determined by dropwise gelation and dehydration phenomena during the printing process. The underlying rationale is that many functional properties of the printed hydrogels are closely associated with the structural characteristics at the sub-droplet and droplet scales, specifically porosity. The porosity of a hydrogel droplet is thought to be determined by intra-droplet fluid–structure interactions during gelation and dehydration. In this study, thus, we characterized the gelation-dehydration and consequent microstructure of thermally responsive poly(<I>N</I>-isopropylacrylamind-<I>co</I>-acrylamide) (PNIPAM) copolymer droplets as a model hydrogel material. The gelation kinetics was studied by differential scanning calorimetry. Both macroscopic and microscopic structures of DOD printed hydrogels were characterized by a 3D profiler and scanning electron microscopy. Furthermore, a theoretical model to explain this complex transport processes was also developed. The results showed that the gelation is a rapid process and its impact is mainly observed at the deposition of droplets. Significant structural shrinkage of the printed hydrogel droplets was induced by dehydration. This shrinkage resulted in spatially varying intra-droplet porosity. A computational model of intra-droplet fluid–structure interactions was developed to explain this spatial variation of intra-droplet porosity. In addition, a new dimensionless parameter is proposed to gauge the significance of evaporation and interstitial water transport in the fluid–structure interactions. Significance of gelation kinetics, dehydration and complex fluid–structure interaction within the droplets was discussed to design a DOD printing process for 3D additive manufacturing of hydrogel-based soft materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Dropwise gelation and dehydration was studied both experimentally and theoretically. </LI> <LI> Dropwise gelation and dehydration during printing process determine the porosity of hydrogel printed. </LI> <LI> An intra-droplet fluid–structure interaction mechanism during printing of hydrogel materials is proposed. </LI> </UL> </P>

Shadow Economy, Tax Evasion, and Transfer Fraud - Definition, Measurement, and Data Problems

Hans-Georg Petersen,Ulrich Thiessen,Pierre Wohlleben 한국국제경제학회 2010 International Economic Journal Vol.24 No.4

The paper tries to shed some light on the definition of the shadow economy, in order to separate shadow activities from market activities and household production. A total income concept is applied, which is based on the labor force being engaged in market, shadow and household activities. Based on such a clear concept, tax evasion can be defined and identified in the market sector and is also usually taking place in the shadow economy, where it is often accompanied by evasion of social security contributions as well as transfer fraud. Money usage in the three sectors is then critically analyzed, and measurement as well as data problems are seriously taken into consideration. The results of our research project suggest that the size of the shadow economy as estimated with the currency approach often yields the highest possible values. Other approaches and plausibility considerations produce much lower values, which seem to be much more realistic. Consequently, policy considerations to strengthen the control mechanisms should be met with utmost skepticism.

Editors' Introduction: Shadow Economy in High Income Countries - Much Ado about Nothing?

Hans-Georg Petersen,Ulrich Thiessen 한국국제경제학회 2010 International Economic Journal Vol.24 No.4

Confucian “Negative Ethics” for a Global World?

Hans-Georg Moeller(한스 게오르그 묄러) 한국동양철학회 2010 동양철학 Vol.0 No.34

최근 유교 윤리학이 당대 세계 사회에서 아직도 유효하게 기능할 수 있는지에 대하여 철학적 토론이 진행되었다. 어떤 이들은 유교의 윤리학은, 특히 가족관계의 중요성을 강조하는 측면에 있어서는, 진정한 근대화에 장애가 될 것이며, 결국 족벌정치나 부패를 정당화 하는 도구로 쓰일 것이라고 주장한다. 이 견해에 따르면 유교는 보편적인 윤리 원칙과 관련된 모든 갈등 상황에서 자기 가족이나 자기가 속한 그룹의 이해를 우선시하는 것을 허용한다. 이 입장을 비판하는 사람들은 공자는 공개적으로 족벌정치나 부패를 옹호한 적이 없었으며, 모든 사람을 감싸는 인자한(仁) 도덕 원리를 반대한 적이 없다는 것을 지적하였다. 그들의 주요 주장은 유교의 도덕가치는 보편타당한 것이고 반드시 가족이나 친구 사이에서만 통행되는 것이 아니라는 것이었다. 이들의 해석에 따르면 인의(仁義)와 같은 덕목은 어떤 서양의 기본적인 도덕 가치와 비교해도 손색없는 보편적인 도덕원칙으로 기능할 수 있다고 한다. 내가 보기에는 유교적 도덕관에 대한 좀 더 강한 변론이 제기될 수 있다고 생각한다. 나는 이 논문에서 유교 윤리학이 서양 도덕 철학의 하나의 대안이 될 수 있다고 주장하고자 한다. 나에게 있어 유교 윤리학은 어떤 보편적인 도덕기준들을 규정하려고 한 것이 아니며, 바로 그렇기 때문에 처음에는 이것이 역설적으로 보일지는 모르겠으나, 이것이 대다수의 서양 도덕 철학보다도 훨씬 더 실천가능하고, 유연하며, ‘보편화 될 수 있는’ 가능성이 있는 것이다. 나는 고금의 서양 ‘근본주의적 윤리’에 대한 유교의 ‘소극적 윤리’의 우월성을 보여주려고 한다. 유교의 ‘소극적 윤리학’은 인간의 우수성은 도덕적 혹은 법률적 기준에 철저하게 복종하는 것으로써(만) 평가될 수 없다고 말한다. 공자에게 있어 ‘탁월한’ 삶을 산다는 것은 단지 도덕적 올바름만 아우르는 것이 아니다. 이런 의미에서 공자는 윤리학의 한계를 주장하며, 나아가 어떤 경우에는 특정한 윤리원칙들을 부정하고 가족이나 친구에 대한 행위자의 감정과 같은 것에 기반한 행위를 더 우선시하는 ‘소극적 윤리학’을 주장하고 있다. 개인적으로 이런 것은 소위 ‘전 세계적인’ 윤리적 원칙들을 세울 것을 요구하는 현대의 광범위한 근본주의적 요구에 관련하여, 혹은 대항하여 매우 추천할 만한 태도라고 사료된다. A recent philosophical debate discussed the question if Confucian ethics could still have a function in contemporary world society. Some described Confucian ethics, particularly with respect to its focus on the importance of family relations, as an impediment for true modernization which, in the final end, would only serve as a justification of nepotism and corruption. According to this view, Confucianism allows for giving precedence to the interests of your family or of the group to which you feel you belong in all cases where those are in conflict with general ethical principles. Critics of this position pointed out that Confucius did not explicitly advocate nepotism, and much less corruption, and that he was not opposed to benevolent moral principles that are binding for everyone. The main argument was that Confucian moral values are indeed universally valid, and not only among family members or friends. Such virtues as humaneness (ren) or righteousness (yi), according to these interpreters, can serve as much as general moral principles as any Western set of basic moral values. In my view, it is possible to come up with a stronger defence of Confucian morality In my view, Confucian ethics did not aim at defining a specific set of universal moral norms, and is precisely therefore, even though this may seem paradoxical at first, much more practical, flexible, and “universalizable” than most Western moral philosophies. I will try to point out the advantages of a Confucian “negative ethics” over traditional and contemporary Western “fundamentalist ethics.” Confucian “negative ethics” says that human excellence cannot be measured by strict obedience to moral or legal norms. Living an excellent life, for Confucius, encompasses more than only ethical correctness. In this sense, Confucius argues for the limitations of ethics, or for a “negative ethics” that negates certain ethical principles in certain situations, and privileges a behavior that is based on, for instance, the feelings one has towards one's family members or friends. I think that this is a very recommendable attitude, particular with respect and in opposition to contemporary demands for a global “fundamentalist” set of supposedly “universal” ethical rules.

Smooth backfitting for additive modeling with small errors-in-variables, with an application to additive functional regression for multiple predictor functions

Han, Kyunghee,Mü,ller, Hans-Georg,Park, Byeong U. Bernoulli Society for Mathematical Statistics and 2018 Bernoulli Vol.24 No.2

<P>We study smooth backfitting when there are errors-in-variables, which is motivated by functional additive models for a functional regression model with a scalar response and multiple functional predictors that are additive in the functional principal components of the predictor processes. The development of a new smooth backfitting technique for the estimation of the additive component functions in functional additive models with multiple functional predictors requires to address the difficulty that the eigenfunctions and therefore the functional principal components of the predictor processes, which are the arguments of the proposed additive model, are unknown and need to be estimated from the data. The available estimated functional principal components contain an error that is small for large samples but nevertheless affects the estimation of the additive component functions. This error-in-variables situation requires to develop new asymptotic theory for smooth backfitting. Our analysis also pertains to general situations where one encounters errors in the predictors for an additive model, when the errors become smaller asymptotically. We also study the finite sample properties of the proposed method for the application in functional additive regression through a simulation study and a real data example.</P>

Musil und das 20. Jahrhundert

( Hans Georg Pott ) 서울대학교 독일어문화권연구소 1993 독일어문화권연구 Vol.2 No.-

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Crystal structure of <i>Arabidopsis thaliana</i> 12‐oxophytodienoate reductase isoform 3 in complex with 8‐<i>iso</i> prostaglandin A₁

Han, Byung Woo,Malone, Thomas E.,Kim, Do Jin,Bingman, Craig A.,Kim, Hyun‐,Jung,Fox, Brian G.,Phillips Jr., George N. Alan R.Liss 2011 Proteins Vol.79 No.11

Die Zivilisationskritik im Spatwerk Goethes

( Hans Georg Pott ) 경남대학교 인문과학연구소 1993 人文論叢 Vol.4 No.-

The contribution and response of microbes to marine environmental change

Hans-Georg Hoppe,Klaus Gocke,Petra Breithaupt 대한지질학회 2007 대한지질학회 학술대회 Vol.2007 No.0

Estimating Needs and Demand for Housing in Developing Countries by Simple Models

Hans de Kruijk,J. George Waardenburg 서울대학교 경제연구소 1979 經濟論集 Vol.18 No.3