Issues and Trends in Cross-border E-commerce in Korea

Consumers purchase cross-border e-commerce products directly from overseas online shopping malls. An increase in the popularity of cross-border e-commerce means that smart consumption trends revolutionized the consumption process. The scale of cross-border e-commerce in Korea reached a record high in 2017. Existing literature suggests that the sharp increase is due to price, product diversity, efficient shipping, expansion of duty-free range and hedonic motivation. A semantic network analysis revealed three main clusters in relationships between cross-border e-commerce research subjects: consumer, country and process

Generalized gravity model for human migration

The gravity model (GM) analogous to Newton's law of universal gravitation has successfully described the flow between different spatial regions, such as human migration, traffic flows, international economic trades, etc. This simple but powerful approach relies only on the 'mass' factor represented by the scale of the regions and the 'geometrical' factor represented by the geographical distance. However, when the population has a subpopulation structure distinguished by different attributes, the estimation of the flow solely from the coarse-grained geographical factors in the GM causes the loss of differential geographical information for each attribute. To exploit the full information contained in the geographical information of subpopulation structure, we generalize the GM for population flow by explicitly harnessing the subpopulation properties characterized by both attributes and geography. As a concrete example, we examine the marriage patterns between the bride and the groom clans of Korea in the past. By exploiting more refined geographical and clan information, our generalized GM properly describes the real data, a part of which could not be explained by the conventional GM. Therefore, we would like to emphasize the necessity of using our generalized version of the GM, when the information on such nongeographical subpopulation structures is available.Comment: 14 pages, 6 figures, 2 table

Fabrication and tuning of plasmonic optical nanoantennas around droplet epitaxy quantum dots by cathodoluminescence

We use cathodoluminescence to locate droplet epitaxy quantum dots with a precision $\lesssim$ nm before fabricating nanoantennas in their vicinity by electron-beam lithography. Cathodoluminescence is further used to evidence the effect of the antennas as a function of their length on the light emitted by the dot. Experimental results are in good agreement with numerical simulations of the structures

Stabilized gold nanorod–dye conjugates with controlled resonance coupling create bright surface-enhanced resonance Raman nanotags

The preparation and characterization of stable and non-aggregated colloidal suspensions of gold nanorod–molecular dye complexes which exhibit very bright surface-enhanced resonance Raman scattering (SERRS) signals is described. A systematic study was performed where both the localized surface plasmon resonance (LSPR) of the nanorod and the molecular resonance of dyes adsorbed onto the rod surface were selectively tuned with respect to the laser excitation wavelengths. Resonance coupling was found to be a significant factor in the overall SERRS enhancement. The polymer stabilized nanorod–dye conjugates were prepared without the added complexity of nanoparticle aggregation as well as having good control over the surface coverage and orientation of the dye molecules. Furthermore, we demonstrate that this new class of Raman nanotags greatly outperforms an approach based on quasi-spherical gold nanoparticles

Effective Control of Pharmaceuticals in Water Using Oxidation Technologies

Environmental EngineeringIn recent years, there has been growing concern about the appearance of pharmaceuticals in surface water as their uses increase. Even though the toxicological effect of low concentrations of pharmaceuticals in drinking water is not yet fully understood, these compounds should be minimized to reduce the risk of unpredictable long term effects based on the precautionary principles. Therefore, ozonation and copper catalyzed Fenton and photo-Fenton are discussed to be potential methods for effective control of pharmaceuticals in this study. In order to establish a practical and mechanistic database for pharmaceutical compounds using these methods, the following issues were investigated in this study. Firstly, the oxidative degradation of pharmaceutical compounds is demonstrated during ozonation of different water samples in Ulsan. Diclofenac, carbamazepine, bezafibrate, and ibuprofen were selected as surrogate pharmaceutical compounds, and ozonation experiments were performed using four different water samples; Surface water samples (Hoeya Dam and Sayeon Dam) are the source of drinking water production in Ulsan. In addition, raw water and water after filtration were collected from the treatment process of Hoeya drinking water plant. Diclofenac and carbamazepine which have high reactivity with molecular ozone showed higher removal efficiencies than bezafibrate and ibuprofen during ozonation. The addition of tert-butanol, a hydroxyl radical scavenger, increased the removal efficiencies of diclofenac and carbamazepine by increasing the ozone exposure. However, the oxidation of bezafibrate and ibuprofen was inhibited by the presence of tert-butanol due to the suppression of the exposure to hydroxyl radical. The elimination of the selected pharmaceuticals could be successfully predicted by the kinetic model base on the Rct concept. Depending on the experimental condition, Rct values were determined to be (1.54~3.32)×10-7 and (1.19~3.04)×10-7 for the Sayeon Dam and the Hoeya Dam waters, respectively. Relatively high Rct values indicate that the conversion of O3 into ˙OH is more pronounced for surface waters in Ulsan compared to other water sources. Furthermore, model prediction of 19 pharmaceutical compounds including diclofenac, carbamazepine, bezafibrate, and ibuprofen was conducted in investigated water samples with various concentrations of ozone dose. Secondly, the degradation of diclofenac and carbamazepine by the copper-catalyzed Fenton and photo-Fenton systems was investigated with respect to several reaction parameters such as pH, scavenger and catalyst concentration. The removal rates of targeted pharmaceutical compounds by the Cu(II)/H2O2 system were found to be gradually increased with rising pH from 3 to 8, but decreased at more alkaline pH. The possible mechanism was discussed based on Fenton chemistry, and two factors are recommended to be attributable for. First, the reduction reaction of Cu(II) is accelerated by the H2O2 and Cu(II) complexation, which favors the reaction of HO2- with Cu(II). Second, oxidants produced by the Cu(II)/H2O2 system are likely shifted from •OH to Cu(III) as pH increases up to the alkaline region, and the oxidants responsible for the degradation of diclofenac and carbamazepine was not Cu(III) but •OH. On the other hand, the rate of pharmaceutical compounds removal by the Cu(II)/H2O2 system were monitored under UV irradiation, and a significant enhancement was observed in the degradation rates at a range of pH (3-10). It is believed that the decomposition of pharmaceuticals is leveled up because of the Cu(II) reduction by HO2• which is produced from H2O2 photolysis. The evidences was shown in the comparison of Cu(II) and H2O2 absorbance at λmax = 365 nm and measurement of Cu(I) conversion rates.ope

Inactivation of planktonic and biofilm cells by copper-based hybrid disinfection systems: Application to biofouling control on RO membranes

Department of Urban and Environmental Engineering (Environmental Science and Engineering)Development of biofilm is easily found in any moist environment, and it causes a number of problems, especially financial losses in the industrial field, when it occurs in undesired places, such as membranes, heat exchanger systems, ship hulls, and drinking water distribution systems. In particular, the formation of biofilm on the membrane surface (biofouling) is one of the biggest challenges to the performance of the reverse osmosis (RO) process. In this dissertation, three different types of copper-based disinfection systems including oxidative disinfectants, biocides, and signal molecule were investigated to control biofilm formed on RO membrane. The first part of the dissertation investigates combinations of Cu(II) with hydroxylamine (HA) and hydrogen peroxide (H2O2) (i.e., Cu(II)/HA, Cu(II)/H2O2, and Cu(II)/HA/H2O2 systems) for the control of Pseudomonas aeruginosa biofilms on RO membranes. These Cu(II)-based disinfection systems effectively inactivated P. aeruginosa cells, exhibiting different behaviors depending on the state of bacterial cells (planktonic or biofilm) and the condition of biofilm growth and treatment (normal or pressurized condition). The Cu(II)/HA and Cu(II)/HA/H2O2 systems were the most effective reagents for the inactivation of planktonic cells. However, these systems were not effective in inactivating cells in biofilms on the RO membranes possibly due to the interactions of Cu(I) with extracellular polymeric substances (EPS), where biofilms were grown and treated in center for disease control (CDC) reactors. Differ from the results using CDC reactors, in a pressurized cross-flow RO filtration unit, the Cu(II)/HA/H2O2 treatment significantly inactivated biofilm cells formed on the RO membranes, successfully recovering the permeate flux reduced by the biofouling. The pretreatment of feed solutions by Cu(II)/HA and Cu(II)/HA/H2O2 systems (applied before the biofilm formation) effectively mitigated the permeate flux decline by preventing the biofilm growth on the RO membranes. The second part of the dissertation utilizes the copper-based system (Cu(II), Cu(II)/HA), which is known as an effective biocide, with norspermidine (Nspd) as a disassembly reagent to control biofilm formed on membrane, and evaluates its potential as a cleaning reagent for biofouling control. Combination with Nspd results in improved inactivation efficacy of the copper-based system in biofilm. In particular, the Cu(II)/HA/Nspd (2.0 log in 10 min) system showed significant enhancement compared to the Cu(II)/HA system (4.2 log in 5 min). The results indicated that disruption of EPS by Nspd contributed to higher penetration of copper rather than detachment of cells under the applied conditions. Furthermore, our finding showed that the combined system is applicable in practical conditions (under pressurized condition) with capable biofilm inactivation efficacy, and a valid degree of permeate flux recovery was also observed, approving the feasibility as a cleaning reagent for biofouling control. The third part of the dissertation assesses the biocidal effects of the Cu(II)-activated persulfate in the presence of chloride ion (i.e., PMS, Cu(II), Cu(II)/PMS, PMS/Cl-, and Cu(II)/PMS/Cl- systems) on planktonic and biofilm cells, and evaluates the feasibility of these disinfection systems in the RO desalination process. The SO4????? was found to be the main produced oxidant via the Cu(II)-activated persulfate system. In addition, the production of sulfate radial likely occurred close to bacteria cells where the Cu(I) was interred, and the produced bacteria-bound sulfate radical would directly damage P. aeruginosa cells. The enhanced inactivation efficacy in the Cu(II)/PMS/Cl- system was attributed to the production of reactive species by a dual mechanism through the Cu(II)/PMS system and the Cu(II)/in situ production of HOCl system.ope

High Temperature VO2 based Microbolometer with Enhanced Light Absorption

Department of Materials Science and EngineeringMicrobolometer depends on the change in electrical resistance of material as the temperature of the material changes. As element technology of microbolometer, VOx thin films are widely used due to high temperature resistance coefficients (TCR) and low noise . However, due to the metal insulator transition (MIT) property of the VO2 thin film, it is difficult to fabricate a micro bolometer at 68oC which can operate at high temperatures. Also, high light absorption is required . Here, we developed VO2 thin films a nd nanowires. And we developed a light absorber to increase the responsivity of microbolometer through high light absorption and applied it to various application. In order to obtain high quality of thermal sensitive material, we fabricated the resistor in cluded in micro bolometer which has a low resistance and a high temperature resistance coefficient (TCR) by growing the tetragonal VO2 crystal phase on the oxide thin film of the perovskite structure. In addition, infrared absorber has multilayer structure in which Ti metal layer and an MgF2 dielectric layer are alternately deposited with a several repetition cycle. The absorber layer shows about 70 % infrared absorption in the range of 8 14 ??m. In this paper, we used VO2 for the TCR material and the infrar ed absorber, showing the enhanced performance compared to that of the conventional micro bolometer. The micro bolometer operates even at high temperature of 100??C. The micro bolometer has a responsivity and detectivity of 4.90 x 10^3 V/W and 1.45 x 10^8 cmHz 1/2 /W at 100oC.clos

Increased arterial stiffness in healthy subjects with high-normal glucose levels and in subjects with pre-diabetes

<p>Abstract</p> <p>Background</p> <p>Increased fasting plasma glucose (FPG), which includes impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and diabetes, is a risk factor for arterial stiffness. While IFG is widely accepted as a cardiovascular risk factor, recent studies have argued that subjects with high-normal glucose level were characterized by a high incidence of cardiovascular disease. The purpose of this study is to investigate the relationship between FPG and arterial stiffness in non-diabetic healthy subjects.</p> <p>Methods</p> <p>We recruited 697 subjects who visited the health promotion center of a university hospital from May 2007 to August 2008. Age, sex, body mass index (BMI), resting heart rate, smoking habits, alcohol intake, exercise, blood pressure, medical history, FPG, lipid profile, high sensitivity C-reactive protein (hs-CRP), and Brachial-ankle pulse wave velocity (ba-PWV) were measured. We performed correlation and multiple linear regression analyses to divide the research subjects into quartiles: Q1(n = 172), 65 mg/dL ≤FPG < 84 mg/dL; Q2(n = 188), 84 mg/dL ≤FPG < 91 mg/dl; Q3(n = 199), 91 mg/dL ≤FPG < 100 mg/dL; Q4(n = 138), 100 mg/dL ≤FPG < 126 mg/dL.</p> <p>Results</p> <p>FPG has an independent, positive association with ba-PWV in non-diabetic subjects after correcting for confounding variables, including age, sex, BMI, blood pressure, resting heart rate, hs-CRP, lipid profile, and behavioral habits. The mean ba-PWV of the high-normal glucose group (Q3, 1384 cm/s) was higher than that of the low-normal glucose group (1303 ± 196 cm/s vs.1328 ± 167 cm/s, P < 0.05). The mean ba-PWV value in the IFG group (1469 ± 220 cm/s) was higher than that in the normoglycemic group (P < 0.05, respectively).</p> <p>Conclusions</p> <p>An increase in FPG, even within the normal range, was associated with aggravated arterial stiffness. Further research is needed to determine the glycemic target value for the prevention of arterial stiffness in clinical and public health settings.</p

Femtomolar detection of Tau proteins in undiluted plasma using surface plasmon resonance

The ability to directly detect Tau protein and other neurodegenerative biomarkers in human plasma at clinically relevant concentrations continues to be a significant hurdle for the establishment of diagnostic tests for Alzheimer’s disease (AD). In this article, we introduce a new DNA aptamer/antibody sandwich assay pairing and apply it for the detection of human Tau 381 in undiluted plasma at concentrations as low as 10 fM. This was achieved on a multichannel surface plasmon resonance (SPR) platform with the challenge of working in plasma overcome through the development of a tailored mixed monolayer surface chemistry. In addition, a robust methodology was developed involving various same chip control measurements on reference channels to which the detection signal was normalized. Comparative measurements in plasma between SPR and enzyme-linked immunosorbent assay (ELISA) measurements were also performed to highlight both the 1000-fold performance enhancement of SPR and the ability to measure both spiked and native concentrations that are not achievable with ELISA