Sung-won Kim

Lamb waves are characterized by their multimodal and dispersive propagation, which often complicates analysis. This paper presents a method for separation of the mode components and reflected components in sensor signals in an active structural health monitoring (SHM) system. The system is trained using linear chirp signals but works for arbitrary excitation signals. The training process employs the cross-Wigner-Ville distribution (xWVD) of the excitation signal and the sensor signal to separate

We demonstrate and compare two phase-insensitive all-optical transistors (AOT's) based on frequency-degenerate quadratic three-wave interactions. In particular, we demonstrate gain using KTP in a type II geometry. Both AOT's exploit the phase insensitivity inherent to three-wave parametric processes when only two fields are input, providing amplification of a small signal at the operating frequency via the interaction with a second-harmonic wave. The first scheme is based on successive up- and d

3GPP LTE is many different from the existing WCDMA based systems. The newness and the complexity of 3GPP LTE physical layer give increment to a number of product development challenges. This paper summarizes the change of physical layer and modulation scheme for 3GPP LTE and shows the simulation and test results of complex LTE physical layer and modulation scheme.

The biohybrid artificial pancreas (BAP), a promising therapy for type 1 diabetes, faces several obstacles such as the need for a large implantation volume of encapsulated islets because of low functionality. To address such problems, in this study we examined long-term insulinotropic activity of glucagon-like peptide-1 (GLP-1)/polymer conjugate [VAPG: poly(N-vinylpyrrolidone-co-acrylic acid-g-PEG) (VAP)-GLP-1] as well as GLP-1/Zn(2+) crystal by coencapsulation with islets. Microcapsules with VAP

Over the last several decades, structural health monitoring systems have grown into increasingly diverse applications. Structural health monitoring excels with large data sets that can capture the typical variability, novel events, and undesired degradation over time. As a result, the efficient storage and processing of these large, guided wave data sets have become a key feature for successful application of structural health monitoring. This article describes a series of investigations into th

In0.4AlAs/In0.35GaAs metamorphic high-electron-mobility transistors (MHEMTs) have been successfully fabricated. In order to reduce the surface effects on the barrier layer, Si3N4 layer passivation by remote plasma-enhanced chemical vapor deposition (PECVD) is utilized, which might suppress the surface trap density in side-recessed region and reduce the parasitic resistance. The device simulation was performed to derive the effects of surface trap in the side-recessed region. As the surface trap

Using a polymeric sulfonylurea (PSU) designed from glibenclamide, we examined the interactions of sulfonylurea with pancreatic islets rather than genetically remodeled beta-cell lines to clarify the biological roles of ATP-sensitive K+ (KATP) channels to which sulfonylurea binds. PSU enhanced insulin secretion from the islets with 10 nM (SU equivalent) treatment, especially at low glucose concentration, but its activity was inhibited by 100 microM diazoxide. Confocal microscopy visualized PSU in

최근 초고층 건물 외벽에는 유리 커튼월 시스템이 많이 적용되고 있으며, 이러한 초고층 건물은 화재 발생 시 연돌효과 및 외부 기류에 따라 수직으로 화재가 급격하게 확산되는 특성을 가지고 있다. 기존에 사용되고 있는 스프링클러헤드는 상층부로의 화재 확산을 효과적으로 방지 할 수 없기 때문에 화재시 막대한 재산 및 인명피해를 초래한다. 따라서 본 연구에서는 보다 넓은 유리커튼월 면적을 방호할 수 있는 수막을 형성하고 층간 화재 확산을 방지 할 수 있는 수막 헤드를 개발하였다. 수막 헤드의 성능을 검증하기 위하여 살수 실험 장치를 구성하고 이를 활용하여 기존 스프링클러 헤드와 살수 패턴을 비교, 분석하였다. 상층부로의 화재 전파 차단 성능을 검토하기 위하여 2층 유리커튼월로 구성되어 있는 실험 장치를 활용하여 화재 실험을 수행하였다. 이를 통해 본 연구에서 제시한 수막 헤드가 기존 스프링클러헤드 보다 효과적으로 화염을 차단하는 것을 확인하였고 수치해석을 통해 최초 크랙 위치 및 파단 임계

Acoustic Emission (AE) based Structural Health Monitoring (SHM) systems are important for impact damage detection and characterization in composite structures. Low velocity impact events can induce internal damage without producing visual indications, compromising the materials structural performance while being very difficult to detect and assess by traditional visual inspection method. Over the years, AE sensor networks have been developed to provide real-time monitoring and detect impact even

In this study, 0.1 µm double-recessed T-gate GaAs pseudomorphic high electron mobility transistors (PHEMT's), in which an InGaAs layer and a Si pulse-doped layer in the cap structure are inserted, have been successfully fabricated. This cap structure improves ohmic contact. The ohmic contact resistance is as small as 0.07 Ωmm, consequently the source resistance is reduced by about 20% compared to that of a conventional cap structure. This device shows good DC and microwave performance such as an

In these days, there are a large number of high-rise buildings constructed with facades (curtain-Pwalls). These facades must be maintained with manual procedures regularly, and each of the periodic procedure is very expensive and risky. For this reason, the interest in developing and employing service robots for the building maintenance has been increased. In this paper, deals with developing a Building Wall Maintenance Robot (BWMR) system based on a guide rail built in curtain-wall. With this B

Structural Health Monitoring (SHM) based on Acoustic Emission (AE) is dependent on both the sensors to detect an impact event as well as an algorithm to determine the impact location. The propagation of Lamb waves produced by an impact event in thin composite structures is affected by several unique aspects including material anisotropy, ply orientations, and geometric discontinuities within the structure. The development of accurate numerical models of Lamb wave propagation has important benefi