• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.618-624
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• 2013

We demonstrated unique inter- and intra-plasmonic coupling effects in bimetallic Au@Ag core-shell NP arrays which are regularly or randomly arranged on self-assembled block copolymer (BCP) inverse micelle monolayers. Polyvinylpyrrolidone (PVP)-stabilized Au@Ag core-shell NP arrays in regular or disordered configuration were incorporated and assembled on reconstructed PS-b-P4VP inverse micelle templates through two types of processes. The intensively enhanced LSPR coupling properties of individual and assembled Au@Ag NPs were evaluated by UV-visible spectroscopy in terms of the type of ligand stabilizer, coupling between Au and Ag, thickness of Ag shell, and type of array configuration. Finally, Au@Ag core-shell NP arrays were employed as active substrates for surface enhanced Raman spectroscopy (SERS) and a significantly enhanced signal enhancement was observed in accordance with the coupling intensity of Au@Ag NPs patterns.

• Journal of Labour Economics
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• v.26 no.2
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• pp.1-30
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• 2003

The recent experience about self-employment shows three main trends: first, its share out of the total workers has steadily increased, recording 37.6% in 2001, implying its prevalence and importance; second, its share out of male workers has caught up female workers', implying its importance to males as well as females; and finally, during the recent Economic Crisis when there was mass layoff and large scale bankruptcy, its share rapidly increased, reflecting its role of a buffer to economic fluctuation. However, there have been few studies on self-employment, mainly focusing on what makes someone choose it as an alternative to being employed. This study analyzes the determinants of the duration to terminate self-employment, by applying the proportional hazard model to the Korea Labor and Income Panel Survey(KLIPS) by the Korea Labor Institute. The KLIPS started the first wave in 1998 with the 5,000 household sample (and about 12,000 individual sample of household members aged 15 and more). In this study, the first four waves are used for analysis. The average duration of 5,357 spells of self-employment is 130 months. It shows slight difference between males(124 months) and females(138 months) while it widely ranges over industries (296 months for agriculture industry while 50 months for restaurant and hotel industry). Estimates of the proportional hazard model of the self-employment duration show that females are more likely to terminate self-employment while it is not statistically significant. The effect of age at starting self-employment on the hazard shows the inverse V-shape, which implies that, until a certain age(47 years), the hazard become higher as aging while, since then, it become lower as aging. The level of education has a positive effect on the hazard, implying that more education is related to the higher probability to be employed. The measures of economic performances, annual sales and earnings, are positively related to continuing self-employment while hardship at the start of self-employment measured by several ways has a negative effect. Training before opening business has a positive effect on keeping on self-employment and its effects are different over its providers, significantly positive for public providers while insignificant for private providers. More and further research on self-employment is urgent in the rapidly ageing society. To help workers to be self-employed, more public assistance is necessary for education, training, financing, marketing, management, and human resource management in order to make the olders consider self-employment as a good alternative rather than an inevitable one.

• Bulletin of the Korean Chemical Society
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• v.23 no.11
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• pp.1595-1603
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• 2002

In this paper we have presented the results of diffusion behavior of model systems for eight liquid n-alkanes ($C_{12}$-$C_{44}$) in a canonical (NVT) ensemble at several temperatures using molecular dynamics simulations. For these n-alkanes of small chain length n, the chains are clearly <$R_{ee}^2$>/6<$R_g^2$>>1 and non-Gaussian. This result implies that the liquid n-alkanes over the whole temperatures considered are far away from the Rouse regime, though the ratio becomes close to the unity as n increases. Calculated self-diffusion constants $D_{self}$ are comparable with experimental results and the Arrhenius plot of self-diffusion constants versus inverse temperature shows a different temperature dependence of diffusion on the chain length. The global rotational motion of n-alkanes is examined by characterizing the orientation relaxation of the end-to-end vector and it is found that the ratio ${\tau}1/{\tau}2$ is less than 3, the value expected for a isotropically diffusive rotational process. The friction constants ${\xi}$of the whole molecules of n-alkanes are calculated directly from the force auto-correlation (FAC) functions and compared with the monomeric friction constants ${\xi}_D$ extracted from $D_{self}$. Both the friction constants give a correct qualitative trends: decrease with increasing temperature and increase with increasing chain length. The friction constant calculated from the FAC's decreases very slowly with increasing temperature, while the monomeric friction constant varies rapidly with temperature. By considering the orientation relaxation of local vectors and diffusion of each site, it is found that rotational and translational diffusions of the ends are faster than those of the center.

• Transactions of Materials Processing
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• v.29 no.5
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• pp.257-264
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• 2020

This paper is concerned with the influence of the plastic property of the rivet on the numerical prediction of the Self-Piercing Rivet (SPR) Joining. In order to predict the plastic property of the rivet, a ring compression specimen was directly fabricated from the rivet used for the mechanical joining of dissimilar materials, and the FE analysis together with the ring compression test was iteratively carried out by changing the plastic property of the rivet. For reliable FE analysis, a friction coefficient was estimated based on a friction calibration curve, measuring the reductions in inner diameter and height of the ring specimen after the compression test. From each simulation result, the force-displacement curves were then compared from each other so as to obtain the rivet plastic property that shows good agreement with the experimental result. The SPR joining between GA590 1.0t and Al5052 2.0t was conducted, and the numerical prediction was performed with the use of the plastic property evaluated based on the inverse analysis and the one referred from Mori et al. [11]. Comparison of the experiment and the numerical predictions in terms of the interlock and bottom thickness revealed that the reliable evaluation of the plastic property of the rivet is necessary for the trustworthy numerical prediction of the SPR joining.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.272.1-272.1
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• 2016

In a three-dimensional topological insulator Bi2Se3, a stress control for band gap manipulation was predicted but no systematic investigation has been performed yet due to the requirement of large external stress. We report herein on the strain-dependent results for Bi2Se3 films of various thicknesses that are grown via a self-organized ordering process. Using small angle X-ray scattering and Raman spectroscopy, the changes of d-spacings in the crystal structure and phonon vibration shifts resulted from stress are clearly observed when the film thickness is below ten quintuple layers. From the UV photoemission/inverse photoemission spectroscopy (UPS/IPES) results and ab initio calculations, significant changes of the Fermi level and band gap were observed. The deformed band structure also exhibits a Van Hove singularity at specific energies in the UV absorption experiment and ab initio calculations. Our results, including the synthesis of a strained ultrathin topological insulator, suggest a new direction for electronic and spintronic applications for the future.

• Journal of Korean Public Health Nursing
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• v.30 no.1
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• pp.56-69
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• 2016

Purpose: The prevalence of problematic internet usage among college students is a cause for concern. There is a lack of study examining influences of cognitive protecting or buffering factors on internet addiction among college students. The purpose of this study was to examine influences of depression, ego-resilience, and active stress coping on internet addiction tendency (IAT) among college students. Methods: A cross-sectional, descriptive design was used. Data were collected between October and December 2013. A convenience sample of 244 students completed self-report questionnaires consisting of Ego-resiliency Scale, Ways of Coping Checklist, Center for Epidemiologic Studies-Depression, and Self-report Scale for Internet Use. Stepwise multiple regression analysis was performed for data analysis. Results: We found that higher levels of depression were associated with higher levels of IAT. However, an inverse association was found between active stress coping and IAT. Students who mainly used the internet for chatting showed lower levels of IAT than those who used the internet for games or blogs. These factors explained 15.1% of the variance in IAT of college students. Conclusion: The study results suggest that stress coping strategies and depression are important factors for evaluation when developing intervention programs targeting college students with problematic internet use.

• Computers and Concrete
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• v.8 no.6
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• pp.735-755
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• 2011

The capability of a multi-directional fixed smeared crack constitutive model to simulate the flexural/punching failure modes of fiber reinforced concrete (FRC) laminar structures is discussed. The constitutive model is implemented in a computer program based on the finite element method, where the FRC laminar structures were simulated according to the Reissner-Mindlin shell theory. The shell is discretized into layers for the simulation of the membrane, bending and out-of-plane shear nonlinear behavior. A stress-strain softening diagram is proposed to reproduce, after crack initiation, the evolution of the normal crack component. The in-plane shear crack component is obtained using the concept of shear retention factor, defined by a crack-strain dependent law. To capture the punching failure mode, a softening diagram is proposed to simulate the decrease of the out-of-plane shear stress components with the increase of the corresponding shear strain components, after crack initiation. With this relatively simple approach, accurate predictions of the behavior of FRC structures failing in bending and in shear can be obtained. To assess the predictive performance of the model, a punching experimental test of a module of a façade panel fabricated with steel fiber reinforced self-compacting concrete is numerically simulated. The influence of some parameters defining the softening diagrams is discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.47-56
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• 1990

An inverse self-iterative procedure is developed to estimate layer moduli and stresses in cement concrete pavement systems from the falling weight deflectometer deflection basins. The existing concrete pavement highways are analyzed using coupled analysis procedure of finite element and layer elastic theory for models obtained through factorial design, from which the characteristics of deflection basins are studied and the empirical equations are proposed for the estimation of layer moduli. The empirical equations are used to assume initial moduli, and the relations between the rate of change of moduli and deflections are used in the self-iterative procedure to ensure accuracy of moduli. The developed computer program of this procedure is verified through various numerical model tests.

• Transactions of Materials Processing
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• v.29 no.5
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• pp.265-271
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• 2020

The purpose of this paper is to analyze the numerical simulation accuracy according to the CFRP modeling method in the CFRP-Al alloy SPR (Self-Piercing Rivet) joint process. The mechanical properties of the CFRP, aluminum sheet are precisely obtained from the tensile test according to the loading direction. Additionally, the hardening curve of rivet was calculated from the inverse analysis of the machined rivet-ring compression test. For the CFRP-Al alloy SPR simulation, two kinds of the CFRP modeling methods were established based on the continuum and layer-by-layer approaches. The simulation results showed that the CFRP layer-by-layer modeling method can provide more reliable prediction shape of the fractured sheets and deformed rivet. This simulation technique can be used in evaluating the CFRP-Metal SPR performance and designing the SPR process conditions.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.114-117
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• 1996

In this study, remote articulation training system which connects the hearing disabled trainee and the speech therapist via B-ISDN is introduced. The hearing disabled does not have the hearing feedback of his own pronunciation, and the chance of watching his speech organs' movement trajectory will offer him the self-training of articulation. So the system has two purposes of self articulation training and trainer's on-line checking in remote place. We estimate the vocal tract articulatory movements from the speech signal using inverse modelling and display the movement trajectory on the sideview of human face graphically. The trajectories of trainees' articulation is displayed along with the reference trajectories, so the trainee can control his articulating to make the two trajectories overlapped. For on-line communication and ckecking training record, the system has the function of video conferencing and transferring articulatory data.