• Geophysics and Geophysical Exploration
• /
• v.14 no.3
• /
• pp.234-241
• /
• 2011

Recently, exploration and development of oil sands are thriving due to high oil price. Because oil sands reservoir usually exists as a thin layer, multicomponent VSP, which has the advantage of the high-resolution around the borehole, is more effective than surface seismic survey in exploring oil sand reservoir. In addition, prestack phase-screen migration is effective for multicomponent seismic data because it is based on an one-way wave equation. In this study, we examined the applicability of the prestack phase-screen migration for multicomponent RVSP data to image the thin oil sand reservoir. As a preprocessing tool, we presented a method for separating P-wave and PS-wave from multicomponent RVSP data by using incidence angle and rotation matrix. To verify it, we have applied the developed wavefield separation method to synthetic data obtained from the velocity model including a horizontal layer and dipping layers. Also, we compared the migrated image by using P-wave with that by using PS-wave. As a result, the PS-wave migrated image has higher resolution and wide coverage than P-wave migrated image. Finally, we have applied the prestack phase-screen migration to the synthetic data from the velocity model simulating oil sand reservoir in Canada. The results show that the PS-wave migrated image describe the top and bottom boundaries of the thin oil sand reservoir more clearly than the P-wave migrated image.

• Journal of Ocean Engineering and Technology
• /
• v.26 no.3
• /
• pp.61-65
• /
• 2012

Air-water flow measurements are of importance for the coastal and ocean engineering fields. Although kinematic investigations of the multi-phase flows have been conducted for long time, velocity measurements still are concerned with many researchers and engineers in coastal and ocean areas. In the present study, an imaging technique using shadowgraphy and fiber optic probe for velocity measurements of air bubbles is introduced. The shadow graphy image technique is modified from the typical image velocimetry methods, and optical fibers are used for the well-known intrusive coupled phase-detection probe system. Since the imaging technique is a non-intrusive optical method from the air, it is usually applied for 2D flows. On the other hand, the double fiber optic probes touch flows regardless of flow patterns. The results of the flow measurements by both methods are compared and discussed. The methods are also applied to the measurements of overtopping flows by a breaking wave over the structure fixed on the free surface.

• Journal of Broadcast Engineering
• /
• v.9 no.4 s.25
• /
• pp.384-390
• /
• 2004

In this paper we compare the performance of 4 different algorithms for converting the sampling frequency of an audio from 44.1KHz to 48KHz. The algorithms considered here include the basic polyphase method. sine function based method. multi-stage method. and B-spline based method. For a fair comparison, the sampling rate converters using the 4 algorithms are redesigned under a high fidelity condition. Then, their H/W complexities are compared in terms of the computational complexity and the memory size. As a result, it is shown that the basic polyphase method and sine function based method outperform the other two in terms of the computational complexity, while the B-spline based method requires less memory than the others.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.04a
• /
• pp.240-244
• /
• 2003

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.04a
• /
• pp.278-281
• /
• 2003

• Korean Journal of Optics and Photonics
• /
• v.15 no.3
• /
• pp.274-277
• /
• 2004

An integrated photonic radio frequency (RF) phase shifter has been proposed and fabricated using a nested dual Mach-Zehnder modulator configuration in a new electro-optic polymer. The fabricated device shows a continuous voltage control of the RF signal phase. A near-linear phase shift exceeding 108$^{\circ}$was obtained for a 16-GHz microwave signal by tuning the do control voltage over a 7.8- $V_{pp}$ range.e.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.439-440
• /
• 2015

한전의 전력계통망에 사용중인 345kV 변압기는 1차와 2차 권선의 일부회로를 공통으로 사용하는 단상 단권변압기를 사용하고 있다. 단상변압기로 인한 3차결선은 변압기 외부에서 알루미늄 부스바를 이용하여 모선을 구성한다. 한편, ${\Delta}$결선의 특징은 3차측 붓싱의 극성과 관련하여 결선방식에따라 3차측 위상이 1차측 위상보다 $30^{\circ}$진상 또는 지상의 위상특성을 가지고 있어 비율차동계전기 결선방식에 있어 주의를 요한다. 변압기는 YNautod1결선 또는 YNautod11으로 결선할 수 있다. 한편 비율차동기용 결선은 1차측과 2차측은 ${\Delta}$결선으로 3차측은 Y결선으로 비율차동계전기에 입력이 되어야 한다. 이때 3차측의 위상을 고려하여 1차측과 2차측의 CT ${\Delta}$결선은 변압기 결선방식과 동일한 결선으로 시행하여 한다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.4
• /
• pp.811-818
• /
• 2016

A continuous fine-tuning phase locked loop with an additional negative feedback loop has been proposed. When the phase locked loop is out-of-lock, the phase locked loop has a fast locking characteristic using the continuous band-selection loop. When the phase locked loop is near in-lock, the bandwidth is narrowed with the fine loop. The additional negative feedback loop consists of a voltage controlled oscillator, a frequency voltage converter and its internal loop filter. It serves a negative feedback function to the main phase locked loop, and improves the phase noise characteristics and the stability of the proposed phase locked loop. The additional negative feedback loop makes the continuous fine-tuning loop work stably without any voltage fluctuation in the loop filter. Measurement results of the fabricated phase locked loop in $0.18{\mu}m$ CMOS process show that the phase noise is -109.6dBc/Hz at 2MHz offset from 742.8MHz carrier frequency.

• Korean Journal of Optics and Photonics
• /
• v.18 no.2
• /
• pp.162-166
• /
• 2007

In this paper, we propose a WDM optical true time-delay (OTTD) beam former for phased way antenna (PAA) systems. It is composed of a delay lines matrix and a multiwavelength source with discrete DFB laser diodes. The building block of a delay lines matrix is a $2\times2$ optical MEMS switch with proper fiber-optic delay line connected between cross ports. A $4\times3$ matrix using four DFB lasers has been fabricated with unit time-delay difference of 12 ps. Maximum time-delay error was measured to be -1.74 ps and +1.14 ps at a radiation angle of $46.05^{\circ}$, corresponding to error range of $-2.87^{\circ}\sim+1.88^{\circ}$. By measuring time-delays at six different RF frequencies from 5- to 10-GHz, we verified the true time-delay characteristic of our OTTD.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.11
• /
• pp.3023-3030
• /
• 2009

In this paper, a prediction and compensation method for the error in the phase measured by using the proportionality between two wavelengths in the TW-PMP (Two-wavelength Phase Measuring Profilometry) is proposed and experimental results are shown to verify the usefulness of the proposed method. For sample object, firstly, a phase-shifting with a quite large number of steps is adopted in measurement, compared with the conventional phase-shifting method, secondly, a 3-3 step phase-shifting method is used to measure the same object which is applied to high-speed 3D shape measurement, and then, measured results from these two phase-shifting methods are compared to calculate measurement noises. From the experimental results applying the proposed compensation method to the measured beat phase and absolute phase, it has proven that noises are decreased by 90% and 17.2% for each case.