• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.477-478
• /
• 2006

Characteristics of InAs/GaAs quantum dot (QD) ridge laser diodes (LDs) are investigated for high-power $1.3\;{\mu}m$ applications. For QD ridge LDs with a $5-{\mu}m$-wide stripe and a 1-mm-long cavity, the emission wavelength of 1284.1 nm, the single-uncoated-facet CW output power as high as 90 mW, the external efficiency of 0.31 W/A and the threshold current density of $800\;mA/cm^2$ are obtained. The linewidth enhancement factor ($\alpha$-factor) is successfully measured to be between 0.4 and 0.6, which are about four times as small values with respect to conventional quantum well structure. It is possible that this result significantly reduce the filamentation of far-field profiles resulting in better beam quality for high power operation.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.1B
• /
• pp.95-109
• /
• 2008

We numerically analyzed the nonlinear shoaling, a plunging breaker and its accompanying energetic suspension of sediment at a bed, and a redistribution of suspended sediments by a down rush of preceding waves and the following plunger using SPH with a Gaussian kernel function, Lagrangian Dynamic Smagorinsky model (LDS), Van Rijn's pick up function. In that process, we came to the conclusion that the conventional model for the tractive force at a bottom like a quadratic law can not accurately describe the rapidly accelerating flow over a swash zone, and propose new methodology to accurately estimate the bottom tractive force. Using newly proposed wave model in this study, we can successfully duplicate severely deformed water surface profile, free falling water particles, a queuing splash after the landing of water particles on the free surface and a wave finger due to the structured vortex on a rear side of wave crest (Narayanaswamy and Dalrymple, 2002), a circulation of suspended sediments over a swash zone, net transfer of sediments clouds suspended over a swash zone toward the offshore, which so far have been regarded very difficult features to mimic in the computational fluid mechanics.

• Proceedings of the Korean Information Science Society Conference
• /
• 1998.10a
• /
• pp.721-723
• /
• 1998

본 논문에서는 기존의 로그구조 디스크 서버(Log-structured Disk Server ; LDS)상에서 부분 세그먼트에 의한 디스크 대역폭 이용률 저하 및 높은 공간 정리 부하(cleaning overhead)량과 같은 문제점을 제기하고, 이러한 부분 세그먼트를 제거하기 위한 방법의 하나로 비휘발성 메모리를 사용한 LDS를 제안한다. 이 새로운 LDS를 Solaris운영체제 상에서 구현하였으며, 다양한 실험을 통하여 제안된 구조가 디스크 대역폭 이용률 및 공간 정리 부하 측면에서 기존의 구조에 비해서 월등히 좋은 성능을 보임을 볼 수 있었다.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.32A no.8
• /
• pp.133-139
• /
• 1995

In this paper, the frequency separation locking and interval stabilization of 4-channel DFB-LDs have been demonstrated using a fiber Fabry-Perot filter with an free spectral range of 100GHz. Frequency fluctuation and locking range of each channel were appeared to be within 15MHz and over 12GHz, respectively. Back-reflection curve from the fiber Fabry-Perot filter was used for the extraction of an error signal in order to increase the number of accomodable channels and extinction ratio.

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.10d
• /
• pp.232-234
• /
• 2002

EEG-based brain computer interface (BCI) provides a new communication channel between human brain and computer. The classification of EEG data is an important task in EEG-based BCI. In this paper we present methods which jointly employ principal component analysis (PCA) and linear dynamical system (LDS) modeling for the task of EEG classification. Experimental study for the classification of EEG data during imagination of a left or right hand movement confirms the validity of our proposed methods.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.8 no.12
• /
• pp.89-95
• /
• 1985

MRP System에서 시스템 성능을 향상시킬 수 있는 하나의 인자는 우수한 Lot-Sizing rule의 선택과 발견이다. 널리 사용되고 있는 Lot-Sizing rule 들 중 Wagner-Whitin 알고리즘은 생산준비 비용과 재고 유지비용이 가변적일 경우 동적 로트크기 결정에 우수한 forward 알고리즘이다. 본 연구에서는 Wagner-Whitin 알고리즘의 중요 원리들을 응용하여 LDS 알고리즘이라 명명한 backward 알고리즘을 개발한다. 그리고 개발된 알고리즘을 Wagner-Whitin 알고리즘과 비교함으로 그 유효성을 테스트하고 backward 알고리즘이 가지는 계산상의 장점을 고찰한다.

• Transactions of the KSME C: Technology and Education
• /
• v.2 no.1
• /
• pp.9-13
• /
• 2014

Nowadays, among several reasons for customers to choose their own cars, NVH performance plays much important role. The concern for the car interior noise is increasing recently, because electric cars and hybrid cars generate less engine noise which was the main noise of traditional cars. According to oversea references, high Lateral Dynamic Stiffness (LDS) of vehicle wheels is described to reduce Structure Bone Noise (SBN) which is being generated while driving cars. However availablet test standards and test results are not enough, in this study the interior noise has been measured after attaching a same tyre to several wheels which has different Lateral Dynamic Stiffness. The test has verified that the interior noise differs depending on Lateral Dynamic Stiffness of wheels. As to this, the reduction of the interior noise can be possible with the optimal design of the wheel.

• The Journal of the Korea Contents Association
• /
• v.7 no.12
• /
• pp.245-253
• /
• 2007

In this paper, we propose an effective web service software platform for remote monitoring and control. We removed the servlet container for better web service performance so as to improve the gSOAP processing which is an essential element of web service implementation. Furthermore, we designed the web service server/client software platform which can be applied to robot or ubiquitous sensor applications. For validation of this study we tested it by manufacturing robot hardware for monitoring control which combined tanks and sensors on a LDS4000 engine board mounted with a PXA270 processor. The practical excellence and the efficiency of the result of this study was validated by the comparison of gSOAP message exchange load between the web service client application and the conventional remote monitoring control technique through a web server.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2002.11a
• /
• pp.481-485
• /
• 2002

In this study, we fabricated the PBH-LD by meltback method using the LPE. The PBH-LDs are analyzed the leakage current that flows through leakage current path like the p-n diode and p-n-p-n current blocking layer. We observed the variation of threshold current with the leakage width $W_{ι}$. As a consequence, we confirmed that the threshold current became low in the decrease of the leakage width and in the increase of the ratio of specific resistivity of leakage region to active region. We also compared between the calculated threshold current in the absence of leakage region and the measured threshold current in the device. As a result, the ratio of specific resistivity was about 0.5 in the measured LDs, which have the width of a active layer of 1.4${\mu}{\textrm}{m}$ and leakage width of 0.6${\mu}{\textrm}{m}$.

• Korean Journal of Optics and Photonics
• /
• v.21 no.2
• /
• pp.74-81
• /
• 2010

A modeling methodology for the analysis of injection-locked Fabry-Perot laser diodes (FP-LDs), promising for cost-effective WDM-PON sources, is proposed. The time-domain large-signal model that is used is found to provide quite similar results to some experimental ones. With our methodology, we model characteristics of FP-LDs, such as influence of reflectivity at a facet and detuning on injection-locking. The eye diagram characteristics are also investigated. It is observed that the facet reflectivity at the injection side should be lower than 1% to provide stable operation in terms of good side-mode suppression ratio and independence from detuning between narrow-band injection noise and LD modes. It is also observed that good eye opening can be obtained for 155 Mbps modulation while the parameters such as the active region thickness should be properly optimized to obtain reasonable eye opening at 1.25 Gbps.