바이어스트라스 점과 굽은 분기점

Thesis (master`s)--서울대학교 대학원 :수학과,2000.Maste

Ridge Regressive Bilinear Model을 이용한 조명변화에 강인한 얼굴 인식

Maste

매끈한 곡선을 세 번 덮는 곡선 위의 선형계

Thesis(doctoral)--서울대학교 대학원 :수리과학부,2006.Docto

Optoelectronic Performance Variations in InGaN/GaN Multiple-Quantum-Well Light-Emitting Diodes: Effects of Potential Fluctuation

We investigate the cause of the optoelectronic performance variations in InGaN/GaN multiple-quantum-well blue light-emitting diodes, using three different samples from an identical wafer grown on a c-plane sapphire substrate. Various macroscopic measurements have been conducted, revealing that with increasing strain in the quantum wells (QWs), the crystal quality improves with an increasing peak internal quantum efficiency while the droop becomes more severe. We propose to explain these variations using a model where the in-plane local potential fluctuation in QWs is considered. Our work is contrasted with prior works in that macroscopic measurements are utilized to find clues on the microscopic changes and their impacts on the device performances, which has been rarely attempted.This work was supported by Industry-University Cooperation Foundation of Hanyang University ERICA

Analysis of carrier recombination dynamics in InGaN-based light-emitting diodes by differential carrier lifetime measurement

In this work, we investigate the carrier recombination dynamics in InGaN-based blue LED devices by analyzing the radiative and nonradiative carrier lifetimes as functions of driving current. To separate the radiative and nonradiative carrier lifetimes, we utilize the information on the internal quantum efficiency (IQE) and differential carrier lifetime. For comparative analysis, the characteristics of the IQE and electroluminescence spectrum are also used. Through measurements and analyses, we demonstrate that the saturation of the radiative recombination rate induced by the phase-space filling in the active volume triggers the increase in nonradiative recombination rate, thus leading to the efficiency droop. (C) 2017 The Japan Society of Applied Physic

Design of automotive engine cooling fan and study on noise reduction through modification of system

Axial fans are widely used for automotive engine cooling device due to their ability to produce high flow rate to keep engine cool. At the same time, the noise generated by these fans causes one of the most serious problems. Especially, engine cooling fan noise in idle condition of a car is noticeable. Therefore, the high efficient and low-noise fan is seriously needed. When a new fan system is designed, system resistance and non-uniform inflow are the key factors to get the high performance and low noise fan system. In this study, experimental study on the fan and system was carried out and brought a successful result of performance and noise from a designed fan. And through the modification of the fan system, the fan produced more flow rate and became less noisy