• Journal of the Society of Naval Architects of Korea
• /
• v.41 no.1
• /
• pp.8-14
• /
• 2004

As the number of offshore structure is glowing in deep waters, there have been increased damages of it. These floating structures in offshore locations exposed to harsh environmental conditions. In recent years, there has been a slowing attention around damages on bow and deck on FPSO caused by waves in steep storm condition. This paper describes a study of the water on deck due to the dynamic behavior of a FPSO with turret mooring system. The nonlinear motions of the FPSO are simulated under external forces due to wave, current, wind, and mooring forces in the time domain. The direct integration method is employed to estimate low frequency drift wave forces. The current forces are calculated by using slow motion maneuvering equations in the horizontal plane. The coefficients of a model for wind forces are calculated from Isherwood's experimental data and the variation of wind speed is estimated by wind spectrum according to the guidelines of API-RP2A.

• Journal of Institute of Control, Robotics and Systems
• /
• v.16 no.7
• /
• pp.720-725
• /
• 2010

In AGPS method, user position can be obtained even in the shadow region by improving signal sensitivity. A hybrid long integration scheme employing both coherent and non-coherent integration method is commonly used in AGPS receivers. Because coherent loss increases as residual frequency become large, residual frequency should be minimized to maximize coherent integration gain. This paper presents performance analysis of residual frequency estimator using FFT in fine-time assistance AGPS method. Considering the hardware complexity and the estimation accuracy, optimal length of FFT is proposed for GPS L1 C/A signal. Signal sensitivity for estimating the residual frequency is also analysed. By field experimental results, it is found that the residual frequency can be successfully estimated using 1 second snap-shot data when GPS signal strength is larger than -150 dBm and its RMS error is 3Hz.

• Journal of the Microelectronics and Packaging Society
• /
• v.4 no.2
• /
• pp.25-32
• /
• 1997

대용량, 고속 정보처리가 요구되는 System의 모듈은 Data 처리의 고속성 및 회로의 고집적이 가능한 MCM의 형태로 구현되어 ATM, GPS 및 PCS 등의 분야에 광범위하게 응 용되고 있다. 위와 같은 High Speed 응용분야에서의 System 성능은 Interconnect Line의 전달지연, 임피던스 부정합에 의한 신호 반사 손실. 신호선 간의 Crosstalk, Ground Bounce 등의 현상에 대한 최적화 여부에 결정적인 영향을 받는다. 그러나 Interconnect의 특성상 정 형이 존재하지 않으므로 추상적인 Library를 구축하는 형식으로 접근할 수밖에 없으며 이를 위하여 여러기본 구조를 정의한후 각 Dimension을 변수로 두고 해석 결과를 합성하여 Database화하는 접근방식이다. 본 논문에서는 MCM-D 공정을 이용하여 Interconnect Line 특성을 분석하고 Database화 하기 위한 Test Pattern을 구현하고 Time Domain reflectometry(TDR)을 이용하여 그특성들을 측정 분석하였다. Test pattern 제작은 MCM-D 공정으로 최소선폭 27$\mu$m, Via Hole 75$\mu$m으로 형성하였고 2 Layer Signal과 GND로 총 3Layer를 구현하였다. 특성분석을 위해 TDR장비와 모데링 및 Simulation S/W인 IPA 510 을 사용하였다. 이를 통해 MCM-D를 이용한 공정에서 Interconcet Line의 고주파 특성을 측정하고 정량화하여 LIbrary를 제작할수 있었다.

• Child Studies in Asia-Pacific Contexts
• /
• v.5 no.1
• /
• pp.21-38
• /
• 2015

This paper reviews Grammatical Mapping theory, a recently proposed theoretical paradigm for understanding children's acquisition of syntax, and ventures to apply the theory to the acquisition of semantics. Particularly, we focused on the domain of space, and proposed how children might acquire a unique system of spatial words in their mother tongue. Based on our review of evidence, we propose that there may be universal semantic primitives that serve as foundations of word meanings. We also propose that children must learn their mother tongue's semantic category system of spatial relations, from real time data. Finally, we argue that children's learning of word meanings may involve creation of a theory that makes sense to the child, and that this process of theory creation is possibly guided by universal principles and parameters.

• Proceedings of the IEEK Conference
• /
• 2006.06a
• /
• pp.181-182
• /
• 2006

Photoconductive three-wire folded dipole antennas for terahertz photomixers have been developed. The folded antennas are characterized by a free space time-domain measurement technique, and the measured data are in good agreement with the simulation results. The folded dipole antennas have much higher antenna resistance than other resonant dipole antennas, implying that they can be used for higher output power of THz photomixers.

• Proceedings of the IEEK Conference
• /
• 2000.07a
• /
• pp.183-186
• /
• 2000

We analyzed the cross-shaped microstripline-fed slot antenna with the reflector using FDTD(Finite-Difference Time-Domain) method in this paper. The proposed antenna uses RR Duroid-5880 substrate(relative permittivity 2.2 and height(1.578 mm) of dielectrics), and compares the optimized results of other kind substrates. The maximum bandwidth of the proposed antenna is from 1.91 GHz to 5.21 GHz, which is approximately 1.437 octave for the VSWR $\leq$ 2. It was found that the bandwidth of the antenna depend highly on the length of the horizontal and vertical feedline as well as the offset position of the feedline. The experimented data for the VSWR and the radiation pattern of the antenna are also represented.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.2
• /
• pp.559-567
• /
• 2018

In this paper, we propose a new load forecasting method for smart air conditioning (A/C) based on the modified thermodynamics of indoor temperature and the unbiased finite memory estimator (UFME). Based on modified first-order thermodynamics, the dynamic behavior of indoor temperature can be described by the time-domain state-space model, and an accurate estimate of indoor temperature can be achieved by the proposed UFME. In addition, a reliable A/C load forecast can be obtained using the proposed method. Our study involves the experimental validation of the proposed A/C load forecasting method and communication construction between DR server and HEMS in a test bed. Through experimental data sets, the effectiveness of the proposed estimation method is validated.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.7A
• /
• pp.705-710
• /
• 2002

In this paper, we present a method to find motion vectors in frequency domain for video data compression. The proposed algorithm is based on the Format Number Transform (FNT), and it declares the most correlated-block as the best matching block, as opposed to declaring the block with least sum of differences between blocks. We show that the proposed method is equivalent to declaring the block with the minimum L2-norm as the best matching block. Unlike other previous fast algorithms, the time requirement for the proposed algorithm does not defend on the image type for finding the optimum solution.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.8 no.3
• /
• pp.21-26
• /
• 2009

The finite element analysis of metal forming processes often fails because of severe mesh distortion at large deformation. As the concept of meshless methods, only nodal point data are used for modeling and solving. As the main feature of these methods, the domain of the problem is represented by a set of nodes, and a finite element mesh is unnecessary. This computational methods reduces time-consuming model generation and refinement effort. It provides a higher rate of convergence than the conventional finite element methods. The displacement shape functions are constructed by the reproducing kernel approximation that satisfies consistency conditions. In this research, A meshless method approach based on the reproducing kernel particle method (RKPM) is applied with metal forming analysis. Numerical examples are analyzed to verify the performance of meshless method for metal forming analysis.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.5 no.4
• /
• pp.47-52
• /
• 1996

The interpolator is very important in CNC machines. This study proposed a parametric curve interpolator(PCI) which can be used for machining any sculptured surface represented in a parametric form and generates commands for tool motion between CAD data points according to given accuracy demands. The proposed interpolator is superior to the existing linear interpolator in accuracy, feed rate and acceleration continuity. Moreover in comparison to the recently developed cubic spline interpolator, the PCI has the capability of handling higher order parametric curves and also ensures precise tracking in the velocity domain. Results from real time simulations and experiments on open architecture CNC machines equipped with the proposed interpolator are presented to show its practical capagility. It is believed that the combination of the proposed interpolator and the open architecture machine controller further advances the area of command generation which is an important aspect of CAD/CAM.