Taeyong Kim

Structural failures caused by a strong earthquake may induce a large number of casualties and huge socioeconomic losses. To design a structure that can withstand such earthquake events, it is essential to accurately estimate the nonlinear structural responses caused by strong ground motions. As a replacement of an onerous and complex nonlinear time history analysis, simple regression-based equations have been widely adopted in routine engineering practices. It is, however, noted that the respons

Organic-inorganic hybrid perovskites exhibiting exceptional photovoltaic and optoelectronic properties are of fundamental and practical interest, owing to their tunability and low manufacturing cost. For practical applications, however, challenges such as material instability and the photocurrent hysteresis occurring in perovskite solar cells under light exposure need to be understood and addressed. While extensive investigations have suggested that ion migration is a plausible origin of these d

The site vacancy responsible for the manifestation of a spontaneous normal-to-relaxor transition was investigated using La-modified PbTiO3 as a model perovskite system. The two cation-site defects relevant to the present study are the A-site (Pb site) and B-site (Ti site) vacancies. To clearly elucidate the type of vacancy involved in the spontaneous transition, we have developed a sintering route that suitably adjusts the relative concentration of these two distinct cation-site vacancies. Using

Summary As urban systems become more highly sophisticated and interdependent, their vulnerability to earthquake events exhibits a significant level of uncertainties. Thus, community‐level seismic risk assessments are indispensable to facilitate decision making for effective hazard mitigation and disaster responses. To this end, new frameworks for pre‐ and post‐earthquake regional loss assessments are proposed using deep learning methods. First, to improve the accuracy of the response prediction

) have recently been reported in disentangled ultra-high molecular weight polyethylene (UHMWPE) films, considerably exceeding prior reported values for oriented films. However, conflicting explanations have been proposed for the microscopic origin of the high thermal conductivity. Here, we report a characterization of the thermal conductivity and mean free path accumulation function of disentangled UHMWPE films (draw ratio ~200) using cryogenic steady-state thermal conductivity measurements and

Abstract The response of a hysteretic system is determined not only by the instantaneous external force but also by the loading history; thereby, a nonlinear time history analysis is needed for the accurate prediction of dynamic responses. The authors recently developed deep neural network (DNN) models for near‐real‐time seismic response predictions of hysteretic systems (Kim et al., 2019). The DNN models outperform existing regression‐based prediction methods for the idealized hysteretic system

Abstract To accurately predict the seismic demands of structural systems, a proper set of ground motions representing the seismic hazard of a given site is needed. In general, such a set includes a large number of ground motions, and thus may result in high computational cost. To address this computational challenge without compromising the accuracy of structural fragility, this paper proposes a clustering‐based algorithm that can select a representative subset of ground motions adaptively from

No abstract available.

Effects of cation-site vacancies on the characteristics of the cubic–tetragonal displacive transitions in La-modified PbTiO3 (PLT) were studied using in situ XRD measurements and Raman scattering. For this purpose, two distinct types of PLT series having cation-site vacancies either at the A site (PLT-A) or at the B site (PLT-B) were separately prepared. The PLT-A series exhibited normal ferroelectricity and underwent the cubic-to-tetragonal structural transition for La substitution up to 30 at.

Molybdenum disulfide (MoS2), a member of transition-metal dichalcogenide family, is of intense interest due to its unique electronic and thermoelectric properties. However, reports of its in-plane thermal conductivity vary due to the difficulty of in-plane thermal conductivity measurements on thin films, and an experimental measurement of the in-plane sound velocity has not been reported. Here, we use time-resolved transient grating spectroscopy to simultaneously measure the in-plane elastic and

The reduction in physical size of the Non-volatile memory (NVM) demands the use of high-k dielectrics due to loss in charge trapping behavior. The large bandgap of Al 2 O 3 (∼7.0 eV) proves it suitable for blocking and tunneling layer, while the high dielectric constant of HfO 2 proves it suitable for charge trapping layer (CTL). In this paper, we propose the application of Al doped HfO 2 used as CTL. The doping concentration has been varied by varying the number of sub-cycles (sequential cycles

Abstract Fragility plays a pivotal role in performance‐based earthquake engineering, which represents the seismic performance of structural systems. To comprehensively understand the structural performance under seismic events, it is necessary to consider uncertainties in the structural model, i.e., epistemic uncertainties. However, considering such uncertainties is challenging due to computational complexity, leading most fragility analyses only to consider the chaotic behavior of ground motion