Seungjin Ryu

Rapid Imaging of Latent Fingerprints Using Biocompatible Fluorescent Silica Nanoparticles

Fluorescent silica nanoparticles (FSNPs) are synthesized through the Stöber method by incorporating silane-modified organic dye molecules. The modified fluorescent organic dye molecule is able to be prepared by allylation and hydrosilylation reactions. The optical properties of as-prepared FSNPs are shown the similar optical properties of PR254A (allylated Pigment Red 254) and have outstanding photostability. The polyvinylpyrrolidone (PVP) is introduced onto the surface of FSNP to enhance the binding affinity of PVP-coated FSNP for latent fingerprints (LFPs) detection. The simple preparation and easy control of surface properties of FSNPs show potential as a fluorescent labeling material for enhanced latent fingerprint detection on hydrophilic and hydrophobic substrates in forensic science for individual identification.

Fragmentation in the Twitter Following of News Outlets The Representation of South Korean Users’ Ideological and Generational Cleavage

In recent years, Twitter emerged as an important news driver as most major news organizations now provide newsfeeds via Twitter. We classified 34 South Korean news outlets based on the pattern of co-following among 709,586 Twitter users. We also had a rare opportunity to match their following behavior with individual-level attributes by relying on supplementary survey data on 1,811 members of an online survey panel. Our results reveal that partisan and generational selectivity sharply polarizes news following on Twitter, suggesting that Twitter is likely to reinforce the existing political divisions in society by reducing the likelihood of chance encounters with the disagreeable views.

Global estimates in Orlicz spaces for the gradient of solutions to parabolic systems

We find not only an optimal regularity requirement on the coefficients, but also a lowest level of regularity on the boundary for the global estimate of the gradient of a parabolic system in the setting of Orlicz spaces.

Elliptic Obstacle Problems with Measurable Coefficients in Non-Smooth Domains

We establish a global weighted W 1, p -regularity for solutions to variational inequalities and obstacle problems for divergence form elliptic systems with measurable coefficients in bounded non-smooth domains.

Calderón–Zygmund estimates for ω-minimizers of double phase variational problems

Abstract We provide Calderon–Zygmund estimates for ω -minimizers of double phase variational problems.

Weighed Estimates for Nonlinear Elliptic Problems with Orlicz Data

We study the Dirichlet problem for a divergence structure elliptic equation of p-Laplacian type that is not necessarily of variational form. A global maximal regularity is obtained for such a problem by proving that the gradient of the weak solution is as globally integrable as the nonhomogeneous term in weighted Orlicz spaces under minimal conditions on the nonlinearity and the domain. We find not only reasonable conditions imposed on the nonlinearity and the domain but also a correct relationship between the associated weight and Young function for such a weighted Orlicz regularity.

The Network of Celebrity Politics: Political Implications of Celebrity Following on Twitter

With the rise of networked media such as Twitter, celebrities’ ability to speak on policy matters directly to the public has become amplified. We investigate the political implications of celebrity activism on Twitter by estimating the political ideology of thirty-four South Korean news outlets and fourteen political celebrities based on the co-following pattern among 1,868,587 Twitter users. We also had a rare opportunity to match their following behavior with individual-level attributes by relying on supplementary survey data on 11,953 members of an online survey panel. Our results reveal that celebrity following on Twitter is ideologically skewed; a vast majority of Korean Twitter users following politically influential celebrities are liberal. Additionally, survey results show that political celebrities are more likely to attract those lacking the ability to process one-sided information in a balanced manner.

Development of Latent Fingermarks on Nonporous and Semiporous Substrates Using Photoluminescent Eu(Phen)2 Complex Intercalated Clay Hybrids with Enhanced Adhesion

In forensic science, developing latent fingermarks using powders is a critical, general method to identify individuals. Photoluminescent Eu(Phen)2 complex intercalated clay hybrids have been used to improve the visualization of fingermarks on nonporous (glass and polymer film) and semiporous (euro and dollar banknotes) substrates. An ion exchange reaction has been successfully used to intercalate Eu(Phen)2 complex ions into the interlayer spacing of two different Na+‐clays, Na+‐montmorillonite and Na+‐hectorite, with different primary particle sizes. To change the surface properties of the obtained hybrid to be more lipophilic, the hydroxyl groups at the edge of the hectorite hybrid were modified with hexadecyltrimethoxysilane via silylation. We investigated the correlation of the size and surface properties of the hybrids with their adhesion to fingermark residues. Fingermarks were successfully visualized using hybrids under UV illumination. In particular, ridge details on semiporous substrates can be more clearly seen using hybrids with smaller primary particles and greater lipophilicity.

Analysis of Waterborne Automotive Refinish Paint for Investigating Insurance Fraud

With increasing the number of vehicles, the accident rate also goes up and the damaged vehicles should be painted as a final repair process. At the painting stage the solvent-based paint causes environmental problems. To overcome these problems waterborne refinish paint is frequently used recently. However, for waterborne refinish, the costs of insurance coverage are too expensive, and insurance reimbursement costs could be burdensome. Because of the high price of aquatic paint treatment, the service shop might charge the malicious service price. In this study, the surfactant of Surfynol 104, which is the component in the paint, was used as an indicator whether the vehicle was painted with waterborne paint. The specimen was quantitatively analyzed to contain 0.38% of the surfactant through the standard addition method with isotope substituted internal standard (IS) of fluranthene-d10 by curie point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS).